Abstract:
A novel glycosyl hydrolase with activities of beta-xylosidase and beta-glucosidase is provided. Said glycosyl hydrolase can convert 7-xylosyltaxane compounds to 7-hydroxyltaxane compounds.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a novel glycosyl hydrolase (GH, also called glycoside hydrolase or glycosidase), the amino acid sequence of said enzyme and the nucleotide sequence encoding the enzyme. Particularly, the enzyme has both β-xylosidase and β-glucosidase activities, and can specifically remove the xylosyl group from 7-xylosyltaxane compounds by hydrolysis. The invention relates to the nucleotide sequence encoding said glycosyl hydrolase of 7-xylosyltaxanes, the amino acid sequence of said enzyme and/or the use of the glycosyl hydrolase-producing strains. 
       BACKGROUND 
       [0002]    Paclitaxel (Taxol&#39;) is mainly produced by species of  Taxus . As one of the important achievements in anticancer drug research of 1990&#39;s, it has attracted worldwide attention since its advent because of its unique anti-tumor mechanism and prominent anti-tumor activities (Kingston D G I, et al. The taxane diterpenoids. In: Herz W, et al. eds.  Progress in the chemistry of organic natural products . New York: Springer-Verlag, 1993, 161-165). It can bind to tubulins, promote the polymerization of tubulins and inhibit the depolymerization thereof, and then hinder the formation of the spindles during the mitosis of cells, such that the cells are stalled in the G2/M phase (Horwitz S B. Taxol (paclitaxel): mechanisms of action.  Ann Oncol.  1994, 5 Suppl.). Currently the paclitaxel has been clinically used as a first-line drug for the treatment of breast, ovarian and non-small cell lung cancers, etc. It is also effective against head and neck cancers, melanoma, colon cancer and HIV-induced Kaposi&#39;s sarcoma. 
         [0003]    The content of paclitaxel in  Taxus  plants is extremely low and it is mainly present in the bark, which portion has the highest content of paclitaxel, at only about 0.02% (U.S. Pat. No. 6,028,206). A 100-year-old  Taxus  tree might yield 3 kg of bark which may provide about 300 mg paclitaxel (Horwitz, S B. How to make taxol from scratch.  Nature  1994, 367: 593-594). Thus, to harvest 1 kg of paclitaxel from barks needs about 3,000 trees, and 3˜4 one-hundred year old trees are cut down to meet the requirement of one patient&#39;s dose. In an alternative method, 10-deacetylbaccatin III with a higher content (up to about 0.1%) is extracted from the leaves of  Taxus baccata  L., etc, and used as the material for semi-synthesis of paclitaxel and its structural analog, taxotere, which is slightly more active and more soluble in water than paclitaxel (Denis J N, et al. A highly efficient, practical approach to natural taxol.  J Am Chem Soc.  1988, 110(17):5917-5919; Horwitz R I. Studies with RP 56976 (Taxotere): A semisynthetic analogue of taxol.  J Nat Cancer Inst.  1991, 83(4):288-291; U.S. Pat. No. 4,814,470). The nursery culture of the shrub yew hybrid species is also believed to be the simplest, renewable and the lowest cost way to obtain paclitaxel. 
         [0004]    In addition to the very little content of paclitaxel, C-7 xylosyltaxane compounds (taxane-xyloside) having a mother nucleus structure of paclitaxel, including 7-beta-xylosyl-10-deacytyltaxol (XDT), 7-beta-xylosyl-10-deacetylcephalomannine (XDC), and 7-beta-xylosyl-10-deacytyltaxol C (XDTC), etc, have been isolated from yew bark, wherein 7-beta-xylosyl-10-deacytyltaxol (XDT) is most abundant (Senilh V, et al. Mise en evidence de nouveaux analogues du taxol extraits de  Taxus baccata. J Nat Prod.  1984, 47:131-137; Rao K V. Taxol and related taxanes. I. Taxanes of  Taxus brevifolia  bark.  Pharm Res.  1993, 10:521-524). For example, XDT, XDC and XDTC could be obtained with the yields of 0.5%, 0.02% and 0.0075%, respectively (EP patent 0,905,130B1). These 7-xylosyltaxane compounds can be hydrolyzed by chemical approaches (U.S. Pat. No. 6,028,206; EP patent 1,298,128B1) or biological approaches (U.S. Pat. No. 5,700,669; CN patent No. 200610046296.6; CN patent No. 200710012698.9) to remove the xylosyl group and generate the corresponding 7-hydroxyltaxanes which can be used in chemical semi-synthesis of paclitaxel or taxotere to enhance the utilization of the source of yew trees and alleviate the imbalance between supply and demand of paclitaxel or its analogues. Comparatively speaking, the chemical approach has some disadvantages, such as relatively low yield, more complicated reaction process and environmental pollution, while the biological approach is more environmentally friendly. 
         [0005]    U.S. Pat. No. 5,700,669A, EP patent 0,668,360B1 and relevant articles (Hanson R L, et al. Enzymatic hydrolysis of 7-xylosyltaxanes by xylosidase from  Moraxella  sp.  Biotechnol Appl Biochem  1997, 26: 153-158) disclosed the hydrolyzing method by use of the bacteria  Moraxella  sp. (ATCC55475),  Bacillus macerans  (ATCC55476),  Bacillus circulans  (ATCC55477) and  Micrococcus  sp. (ATCC55478) to convert C-7 xylosyltaxanes into C-7 hydroxyltaxanes, among which the  Moraxella  sp. strain showed the highest conversion ability. Adding 0.5 mg 7-xylosyl-10-deacytyltaxol (XDT) to 2 ml of cell suspension (wet cells, 91.5 mg/ml; XDT, 0.25 mg/ml), the suspension was mixed end-over-end at 12 rpm for 21 h at 28° C. The reaction was then stopped with methanol and the sample was assayed by HPLC. No XDT was found to be remaining and the yield of 10-deacytyltaxol (DT) was 0.23 mg/ml. 
         [0006]    CN patent (No. 200610046296.6) and relevant article (Hao D C, et al. Bacterial diversity of  Taxus rhizosphere : culture-independent and culture-dependent approaches.  FEMS Microbiol Lett  2008, 284:204-212) disclosed a hydrolyzing method to convert C-7 xylosyltaxanes to C-7 hydroxyltaxanes using  Leifsonia shinshuensis  DICP 16 (CCTCC No. M 206026). Similar culturing and converting conditions as those described in above-mentioned US patent is adopted, and 1 mg XDT was added to 2 ml cell suspension. After reacting at 100 rpm for 21 h at 30° C., the reaction was terminated with 2 ml methanol. No XDT was found to be remaining in the reaction solution by HPLC and 0.4 mg/ml DT was produced. In another experiment, different concentrations of 7-xylosyl-10-deacetylbaccatin III (0.5, 0.9, 1.95, 3.1, 4.4, 5.2, and 6.75 mg/ml) were respectively added into 2 ml reaction solution in which the concentration of wet cells was 231.58 mg. The reaction was conducted at 31° C. and 120 rpm for over 40 h. The yield of 10-deacetylbaccatin III reached its highest yield when the concentration of the substrate is 1.95 mg/ml (Hao D C, et al. Bacterial diversity of  Taxus rhizosphere : culture-independent and culture-dependent approaches.  FEMS Microbiol Lett  2008, 284:204-212). 
         [0007]    Another CN patent No. 200710012698.9 disclosed the actinomycete strain  Cellulosimicrobium cellulans  (XZ-5CCTCC No. M 207130), the hydrolase and their use in the conversion of taxanes: 10 ml XDT (with a concentration of 5 mg/ml) was added into 90 ml crude enzyme solution (1 ml of the  Cellulosimicrobium cellulans  seed solution cultured at 30° C. for 2 days was introduced into 100 ml medium and cultured at 30° C., 150 rpm for 5 days, and the resultant was centrifuged and the supernatant was isolated to yield the so-called crude enzyme solution) and the reaction was conducted at 30° C. at 50 rpm for 20 h to yield 40 mg DT. 
         [0008]    Overall, all the biological approaches mentioned above have potential application values in the hydrolysis of 7-xylosyltaxanes. However, the yields are not high enough to meet the requirement of the industrial mass production, due to the ubiquitous low amount of enzyme in the cells and low substrate solubility in water in the prior arts. 
         [0009]    Several kinds of β-xylosidases have been isolated from fungi and other organisms (Tuohy M G, et al. The xylan-degrading enzyme system of  Talaromyces emersonii : novel enzymes with activity against aryl beta-D-xylosides and unsubstituted xylans.  Biochem J.  1993, 290 (Pt 2):515-523; Golubev A M, et al. Purification, crystallization and preliminary X-ray study of β-xylosidase from  Trichoderma reesei. Acta Crystallogr D Biol Crystallogr.  2000, 56 (Pt 8):1058-1060; Pan I, et al. Effective extraction and purification of beta-xylosidase from  Trichoderma koningii  fermentation culture by aqueous two-phase partitioning.  Enzyme Microb Technol.  2001, 28 (2-3):196-201; Rizzatti A C S, et al. Purification and properties of a thermostable extracellular β-D-xylosidase produced by a thermotolerant  Aspergillus phoenicis. J Ind Microbiol Biotechnol.  2001, 26(3):156-160; Saha B C. Purification and characterization of an extracellular β-xylosidase from a newly isolated  Fusarium verticillioides. J Ind Microbiol Biotechnol.  2001, 27 (4):241-245; Gargouri M, et al. Fungus beta-glycosidases: immobilization and use in alkyl-beta-glycoside synthesis.  J Mol Catal B: Enzym.  2004, 29, Issues 1-6:89-94; Lama L, et al. Purification and characterization of thermostable xylanase and β-xylosidase by the thermophilic bacterium  Bacillus thermantarcticus. Res Microbiol.  2004, 155(4):283-289; Belfaquih N &amp; Penninckx M J. A bifunctional β-xylosidase-xylose isomerase from  Streptomyces  sp. EC 10 . Enzyme Microb Technol.  2000, 27(1-2): 114-121), and some β-xylosidase genes (such as those from several fungus sources) have been cloned and identified successfully (Margolles-Clark E, et al. Cloning of genes encoding alpha-L-arabinofuranosidase and beta-xylosidase from  Trichoderma reesei  by expression in  Saccharomyces cerevisiae. Appl Environ Microbiol.  1996, 62(10):3840-3846.; van Peij N N, et al. β-Xylosidase activity, encoded by xlnD, is essential for complete hydrolysis of xylan by  Aspergillus niger  but not for induction of the xylanolytic enzyme spectrum.  Eur J Biochem.  1997, 245 (1):164-173; Perez-Gonzalez J A, et al. Molecular cloning and transcriptional regulation of the  Aspergillus nidulans  xlnD gene encoding a β-xylosidase.  Appl Environ Microbiol.  1998, 64(4):1412-1419; Kitamoto N, et al. Sequence analysis, overexpression, and antisense inhibition of a β-xylosidase gene, xylA, from  Aspergillus oryzae  KBN616 . Appl Environ Microbiol.  1999, 65(1):20-24; Berrin J G, et al. High-level production of recombinant fungal endo-β-1,4-xylanase in the methylotrophic yeast  Pichia pastoris. Protein Expr Purif.  2000, 19(1): 179-187; Reen F J, et al. Molecular characterisation and expression analysis of the first hemicellulase gene (bxl1) encoding β-xylosidase from the thermophilic fungus  Talaromyces emersonii. Biochem Biophys Res Commun.  2003, 305(3):579-585; Kurakake M, et al. Characteristics of transxylosylation by beta-xylosidase from  Aspergillus awamori  K4 . Biochim Biophys Acta.  2005, 1726(3):272-279; Wakiyama M, et al. Purification and properties of an extracellular β-Xylosidase from  Aspergillus japonicus  and sequence analysis of the encoding gene.  J Biosci Bioeng.  2008, 106(4):398-404). However, none of these (natural or recombinant) β-xylosidases was found to have the ability of specifically hydrolyzing 7-xylosyltaxanes. Therefore it is reasonably believed that the genes of β-xylosidases with specific catalytic activity against 7-xylosyltaxane compounds have not been cloned so far, not to mention functional analysis. In fact, a lot of commercial xylosidases, xylanases and other glycosidase did not reveal the ability to remove the xylosyl group from 7-xylosyltaxanes at all (Hanson R L, et al. Enzymatic hydrolysis of 7-xylosyltaxanes by xylosidase from  Moraxella  sp.  Biotechnol Appl Biochem  1997, 26: 153-158). 
       SUMMARY OF THE INVENTION 
       [0010]    In view of the above-mentioned problems present in the prior arts, the object of this invention is to provide a novel and efficient hydrolase that can specifically hydrolyze the xylosyl group from 7-xylosyltaxanes as well as its gene sequences. 
         [0011]    To solve the above-mentioned technical problem, the inventors of the invention made a lot of investigation. Firstly, the specific glycosyl hydrolase (GH) of 7-xylosyltaxanes was purified from the fungi M95.33, which showed specific β-xylosidase activity and could convert 7-xylosyltaxanes to 7-hydroxyltaxanes. The purified enzyme was subjected to LC-MS/MS De novo sequencing and amino acid sequences of some oligopeptides were obtained. Based on amino acid sequences of these oligopeptides, a series of degenerate primers were designed. The cDNA and the structural genes of said enzyme were cloned by molecular biological techniques including nested PCR, RACE, and Genome Walking. The cDNA fragment of the open reading frame (ORF) encoding such enzyme was connected to a suitable expression vector to construct a recombinant plasmid, which was introduced into a corresponding host cell, such as  Pichia pastoris , which grew fast and could be used for high density fermentation. The recombinant strain could catalyze the glycosyl hydrolysis reaction of 7-xylosyltaxanes in high efficiency to produce 7-hydroxyltaxanes. The inventors have also discovered that this enzyme is a bifunctional enzyme, which can remove the glucose residue from the glucoside by hydrolysis. 
         [0012]    This nucleotide sequence exhibits nearly no homology with any other nucleotide sequences that have been registered in GenBank, and the closest sequences are mostly the hypothetical protein gene sequences with the coverage rate of only 3˜7% therebetween. The amino acid sequence deduced from the nucleotide sequence is closest to the hypothetical protein sequence (GenBank accession: XP — 760179) of  Ustilago maydis , presenting 43% identity and 59% similarity in a comparable range. 
         [0013]    The present invention includes the following contents: 
         [0014]    A novel glycosyl hydrolase of 7-xylosyltaxanes, denoted herein as LXYL-P1, is provided. 
         [0015]    The second purpose of the present invention is to provide the nucleotide sequence encoding the enzyme. 
         [0016]    The third purpose of the present invention is to provide a recombinant plasmid containing the nucleotide sequence. 
         [0017]    The forth purpose of the present invention is to provide a host cell containing such a recombinant plasmid or the nucleotide sequence. 
         [0018]    The fifth purpose of the present invention is to provide the use of such an enzyme. 
         [0019]    To realize the purposes of the present invention, the following technical solutions are adopted. 
         [0020]    The present invention provides a glycosyl hydrolase (a bifunctional β-xylosidase-β-glucosidase) of 7-xylosyltaxanes, denoted herein as LXYL-P1. 
         [0021]    The amino acid sequence of the glycosyl hydrolase (LXYL-P1) of 7-xylosyltaxanes comprises, 
         [0000]    an amino acid sequence exhibiting at least 30% identity with the sequence as shown in SEQ ID NO: 2;
 
preferably an amino acid sequence exhibiting at least 40% identity with SEQ ID NO: 2;
 
more preferably an amino acid sequence exhibiting at least 50% identity with SEQ ID NO: 2;
 
further preferably an amino acid sequence exhibiting at least 60% identity with SEQ ID NO: 2;
 
further preferably an amino acid sequence exhibiting at least 70% identity with SEQ ID NO: 2;
 
further preferably an amino acid sequence exhibiting at least 80% identity with SEQ ID NO: 2;
 
further preferably an amino acid sequence exhibiting at least 90% identity with SEQ ID NO: 2;
 
further preferably an amino acid sequence exhibiting at least 95% identity with SEQ ID NO: 2.
 
         [0022]    Or, the enzyme is a protein derived from SEQ ID NO: 2 by substitution, deletion or addition of one or several amino acid residues in the amino acid sequence of SEQ ID NO: 2 and having the same activity as that of the amino acid residue sequence of SEQ ID NO: 2. 
         [0023]    The present invention also provides a nucleotide sequence or a coding gene encoding said glycosyl hydrolase (LXYL-P1) of 7-xylosyltaxanes, denoted as Lxyl-P1. The nucleotide sequence comprises, 
         [0000]    a nucleotide sequence exhibiting at least 30% identity with the nucleotide sequence as shown in SEQ ID NO: 1 or SEQ ID NO: 3;
 
preferably, a nucleotide sequence exhibiting at least 40% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
more preferably, a nucleotide sequence exhibiting at least 50% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
further preferably, a nucleotide sequence exhibiting at least 60% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
further preferably, a nucleotide sequence exhibiting at least 70% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
further preferably, a nucleotide sequence exhibiting at least 80% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
further preferably, a nucleotide sequence exhibiting at least 90% identity with SEQ ID NO: 1 or SEQ ID NO: 3;
 
further preferably, a nucleotide sequence exhibiting at least 95% identity with SEQ ID NO: 1 or SEQ ID NO: 3.
 
         [0024]    Or, the present invention provides a gene from filamentous fungi, which hybridizes under stringent conditions to all or part of the DNA as shown in SEQ ID NO: 1 or SEQ ID NO: 3, or to all or part of a DNA complementary to the sequence as shown in SEQ ID NO: 1 or SEQ ID NO: 3, and which encodes a protein having the activity of hydrolyzing the xylosyl group from 7-xylosyltaxanes. 
         [0025]    The present invention also provides a recombinant plasmid containing the nucleotide sequence and encoding LXYL-P1. Said plasmid can be introduced into proper host cells. 
         [0026]    The present invention further provides proper host cells that may carry the Lxyl-p1 gene sequence, which comprises a nucleotide sequence exhibiting at least 30% identity with that shown in SEQ ID NO: 1 or SEQ ID NO: 3. The host organisms thereof may be homologous producing hosts of the peptide (LXYL-P1) comprising an amino acid sequence that exhibits at least 30% identity with that shown in SEQ ID NO: 2, or, they may be heterologous host cells. 
         [0027]    Suitable host organisms are selected from bacteria, actinomycetes, yeasts, filamentous fungi, plant cells, or animal cells. 
         [0028]    Preferred bacteria are selected from  Escherichia  species,  Bacillus  species; 
         [0000]    preferred actinomycetes are selected from  Streptomyces  species;
 
preferred yeasts are selected from  Saccharomyces  species,  Pichia species  and  Schizosaccharomyces  species;
 
preferred filamentous fungi are selected from  Aspergillus  species,  Trichoderma species, Penicillium  species,  Tricholoma  species,  Lentinula  species, and  Agaricus  species;
 
preferred plant cells are selected from dicotyledon;
 
preferred animal cells are selected from insect cells.
 
         [0029]    A preferred  Escherichia  species is preferably  E. coli;    
         [0030]    A preferred  Bacillus  species is preferably  B. subtilis;    
         [0031]    A preferred  Streptomyces  species is preferably  S. lividans;    
         [0032]    A preferred  Saccharomyces  species is preferably  Saccharomyces cerevisiae;    
         [0033]    A preferred  Pichia  species is preferably  P. pastoris;    
         [0034]    A preferred  Schizosaccharomyces  species is preferably  Schizosaccharomyces pombe;    
         [0035]    Preferred  Aspergillus  species are preferably  A. niger, A. oryzae , and  A. nidulans;    
         [0036]    Preferred  Trichoderma  species are preferably  T. reesei  and  T. viride;    
         [0037]    A preferred  Penicillium  species is preferably  Penicillium chrysogenum;    
         [0038]    A preferred  Tricholoma  species is preferably  Tricholoma mongolicum;    
         [0039]    A preferred  Lentinula  species is preferably  L. edodes;    
         [0040]    A preferred  Agaricus  species is preferably  Agaricus bisporus;    
         [0041]    A preferred dicotyledon is preferably  Arabidopsis thaliana;    
         [0042]    Preferred insect cells are preferably  Spodoptera frugiperda  Sf9 cells. 
         [0043]    The present invention also provides the nucleotide sequence of this invention, the glycosyl hydrolase of 7-xylosyltaxanes of this invention and the use of host cells comprising the nucleotide sequence of this invention. 
         [0044]    In particular, said use is described as follows: suitable host cells were transformed with said DNA by conventional methods in the field, and various substrates, especially the glycoside compounds, are hydrolyzed through the recombinant enzyme produced by the recombinant cells after transformation. 
         [0045]    Preferred glycoside compounds to be used as the substrates are selected from compounds comprising the xylosyl residue or compounds comprising the glucosyl residue; that is, the use of the present invention is to remove the xylosyl and/or glucosyl groups from these glycoside compounds by hydrolysis. 
         [0046]    Preferred compounds with the xylosyl residue are selected from taxane-xyloside compounds; the substrates are preferably taxane compounds containing the 7-xylosyl residue, that is, 7-xylosyltaxanes, which may be formed naturally, or non-naturally, for example, by means of chemical synthesis, biosynthesis or semi-synthesis. 
         [0047]    As an application of the glycosyl hydrolase of 7-xylosyltaxanes in the present invention, it is preferably used in bioconversion or biocatalysis of 7-xylosyltaxanes to prepare 7-hydroxyltaxanes. 
         [0048]    The 7-xylosyltaxanes to be used as the substrates comprise but are not limited to the following compounds: 7-xylosyl-10-deacetyltaxol, 7-xylosyl-10-deacetylcephalomannine, 7-xylosyl-10-deacetyltaxol C, 7-xylosyl-10-deacetyl-baccatin III, 7-xylosyltaxol, 7-xylosylcephalomannine, 7-xylosyltaxol C, 7-xylosylbaccatin III. The products obtained by hydrolysis after removing the xylosyl group comprise, but are not limited to, the following compounds: 10-deacetyltaxol, 10-deacetylcephalomannine, 10-deacetyltaxol C, 10-deacetyl-baccatin III, paclitaxel, cephalomannine, taxol C, and baccatin III. 
         [0049]    These substrates may be used alone or in combination with each other or in a mixture with other taxanes. 
         [0050]    The substrates described herein may be selected from a mixture of xylosyl-containing taxane compounds. The mixture includes, but is not limited to, the plant tissues of the  Taxus  genus, which is preferably selected from  T. baccata, T. brevifolia, T. wallichiana, T. media, T. chinensis, T. yunnanensis , and  T. cuspidate , or the cell cultures of these plants, or cell cultures of 7-xylosyltaxane-producing microorganisms. The plant tissues described herein include the roots, needles, bark and whole seedling of the plant. 
         [0051]    The structural features of paclitaxel or its analogues (products) prepared by the method provided in this invention and the C-7-xylosyltaxane material (substrate) as used, are shown in formula I: 
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 Formula I 
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
          
           
               
                 Compounds 
                 R 
                 R 1   
                 R 2   
                 MW 
               
               
                   
               
               
                 7-Xylosyl-10-deacetyltaxol, XDT 10-Deacetyltaxol, DT 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 H 
                 943 811 
               
               
                   
               
               
                 7-Xylosyltaxol, XT Paclitaxel 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Ac 
                 985 853 
               
               
                   
               
               
                 7-Xylosyl-10-deacetylcephalomannine, XDC 10-Deacetylcephalomannine, DC 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 H 
                 921 789 
               
               
                   
               
               
                 7-Xylosylcephalomannine, XC Cephalomannine 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Ac 
                 963 831 
               
               
                   
               
               
                 7-Xylosyl-10-deacetylbaccatin III, XDB 
                 Xylose 
                 H 
                 H 
                 676 
               
               
                 10-Deacetylbaccatin III, DB 
                 H 
                   
                   
                 544 
               
               
                 7-Xylosyl-baccatin III, XB 
                 Xylose 
                 H 
                 Ac 
                 718 
               
               
                 Baccatin III 
                 H 
                   
                   
                 586 
               
               
                   
               
               
                 7-Xylosyl-10-deacetyltaxol C, XDTC 10-Deacetyltaxol C, DTC 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 H 
                 937 805 
               
               
                   
               
               
                 7-Xylosyltaxol C, XTC Taxol C, TC 
                 Xylose H 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 Ac 
                 979 847 
               
               
                   
               
               
                 Note: 
               
               
                 wherein Ph is phenyl; Bz is benzoyl; Ac is acetyl. 
               
             
          
         
       
     
         [0052]    The solvents used to dissolve the substrates may be selected from: water, methanol, ethanol, ethyl acetate, acetone, n-hexane, chloroform, dichloromethane, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). 
         [0053]    The application of the present invention also includes that the glycosyl hydrolase of this invention is used to improve properties of bread dough, improve properties of animal feed, produce D-xylose for manufacture of xylitol, and deink recycled paper. The glycosyl hydrolase of the present invention may further be used in combination with cellulases and hemicellulases to hydrolyze lignocelluloses to obtain monosaccharides for further manufacture of biofuels, such as ethanol and butanol. The glycosyl hydrolase of the present invention may further be used to release bioactive molecules from other glycoside compounds, which may be applied in the pharmaceutical field. 
         [0054]    The present invention also provides a bioconversion method for the preparation of paclitaxel and its analogues: 7-xylosyltaxanes are used as the starting materials, and the xylosyl groups of the starting materials are removed by hydrolysis by the host cells containing the gene sequence of the present invention, or by the enzyme produced by the host cells, to obtain paclitaxel or its analogues. The preferred host cells are the fungus or the recombinant strains of the family Tricholomareceae; more preferred host cells are the yeast cells of  Pichia pastoris  of the genus  Pichia.    
         [0055]    In summary, the amino acid sequence of the bifunctional glycosyl hydrolase provided by the present invention comprises an amino acid sequence exhibiting at least 30% identity with the sequence as shown in SEQ ID NO: 2. The bifunctional GH provided by the present invention can be used to remove the xylosyl residue or glucosyl residue from 7-xylosyltaxanes or other glycoside compounds. The present invention also relates to the recombinant plasmids and the host cells, both of which containing the nucleotide sequences as described above. Furthermore, the present invention relates to the application of the glycosyl hydrolase of 7-xylosyltaxanes or the host cells containing the glycosyl hydrolase of 7-xylosyltaxanes in removing the xylosyl group and/or glucosyl group by hydrolysis. 
         [0056]    The glycosyl hydrolase of 7-xylosyltaxanes provided by the present invention, which has a definite amino acid sequence and bifunctional properties of β-xylosidase-β-glucosidase, is produced by  Lentinula edodes  M95.33, a fungus of the family Tricholomareceae, or by the recombinant cells containing the coding gene of the enzyme. The enzyme may be present in the cells or secreted outside of the cells and can be used for the conversion of 7-xylosyltaxanes to paclitaxel or its analogues. 
         [0057]    The nucleotide sequence encoding the glycosyl hydrolase according to this invention includes a complete open reading frame (ORF), which may be used to construct varied types of recombinant expression plasmids that can be transferred into the original fungus or other fungal hosts, or be transferred into prokaryotic cells (including  E. coli , actinomycetes), plant cells and animal cells, and the like host cells. These hosts may acquire the ability of hydrolyzing 7-xylosyltaxanes into 7-hydroxyltaxanes due to the expression of the glycosyl hydrolase gene. The recombinant hosts may also be used for biotransformation of other sugar-containing compounds. 
         [0058]    The application of the present invention also includes that the glycosyl hydrolase of this invention is used to improve properties of bread dough, improve properties of animal feed, produce D-xylose for manufacture of xylitol, and deink recycled paper. Furthermore, the glycosyl hydrolase provided by the present invention may be used in combination with cellulases and hemicellulases and so on to hydrolyze lignocelluloses to obtain monosaccharides for further manufacture of biofuels, such as ethanol and butanol. Moreover, the glycosyl hydrolase of the present invention may be used to release the bioactive molecules from other glycoside compounds, which may be applied in the pharmaceutical field. 
       THE BENEFICIAL TECHNICAL EFFECTS 
       [0059]    The present invention has cloned and heterologously expressed, for the first time, the gene encoding a glycosyl hydrolase that may specifically catalyze 7-xylosyltaxanes to 7-hydroxyltaxanes, and has constructed the bio-engineered strains having the activity of such enzyme, and thus provides a novel and effective way for the large-scale production of 7-hydroxyltaxanes. 
       TERMS AND ABBREVIATIONS 
       [0060]    CDS: the coding sequence of a protein, which is from the start codon to the stop codon. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0061]      FIG. 1 : Phenyl Sepharose hydrophobic column chromatography of the β-xylosidase-β-glucosidase from the protein extract of the fungus M95.33 (A), and thin layer chromatography (TLC) of XDT conversion (B).
       A: P1. active elution peak of LXYL-P1; P2. active elution peak of LXYL-P2. The horizontal ordinate shows different fractions (numberings of collecting tubes of different fractions), and the vertical axis is absorption value of A405 (405 nm)   B: 1. XDT (control); 2. DT (control); 3. XDT bioconversion by LXYL-P1; 4. XDT bioconversion by LXYL-P2.       
 
           [0064]      FIG. 2 : Electrophoresis (SDS-PAGE) of the LXYL-P1.
       1. molecular weight marker of protein; 2. LXYL-P1 treated by reduction; 3. LXYL-P1 treated by non-reduction. The protein band for LC-MS/MS analysis is shown by the arrow.         
           [0066]      FIG. 3 : Agarose gel electrophoresis of colony PCR identification on the recombinant yeasts.
       M. molecular marker; 1. the recombinant strain GS115-9K (control, transformed with pPIC9K); 2. the recombinant strain GS115-9K-P1-2 (transformed with pPIC9K-P1-2); 3. the recombinant plasmid pPIC9K-P1-2 (control).         
           [0068]      FIG. 4 : Comparison of the recombinant strains GS115-9K-P1-2 and GS115-9K (control) on β-xylosidase activity. 
           [0069]      FIG. 5 : HPLC analysis of XDT conversion by the recombinant strain GS115-9K-P1-2.
       A. before conversion; B. after conversion.         
           [0071]      FIG. 6 : HPLC analysis of conversion of 7-xylosyltaxane mixtures by the recombinant strain GS115-3.5K-P1-2.
       A. the mixed substrates (control); B. recombinant yeast GS115-3.5K introduced with a null vector (pPIC3.5K)+the mixed substrate (control); C. recombinant yeast GS115-3.5K-P1-2 introduced with the plasmid pPIC3.5K-P1-2 harboring Lxyl-p1 gene+the mixed substrate. 1, 2 and 3 represent 7-xylosyl-10-deacetylcephalomannine (XDC), 7-xylosyl-10-deacetyltaxol (XDT), and 7-xylosyl-10-deacetyltaxol C (XDTC), respectively; and 1′, 2′ and 3′ represent the corresponding products of xylosyltaxane, i.e., 10-deacetylcephalomannine (DC), 10-deacetyltaxol (DT), and 10-deacetyltaxol C (DTC), respectively.         
           [0073]      FIG. 7 : HPLC analysis of conversion of 7-xylosyl-10-deacetylbaccatin III by the recombinant strain GS115-3.5K-P1-2 (the solvent peak with a retention time of 2 min is prior to XDT). 
           [0074]      FIG. 8 : Schematic diagram of the PCR amplification process 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0075]    The present invention is further illustrated by the following examples which are illustrative only and which are by no means meant to limit the scope of the present claims. 
       Example 1 
     Purification of  L. edodes  β-xylosidase-β-glucosidase (LXYL-P1) 
       [0076]    Cultivation of the fungus M95.33. 
         [0077]    About 1 cm 2  of lawn picked from a mycelial slant after cultivation was inoculated and grown in 100 ml sterile wheat bran liquid medium [contains per liter: 50.00 g wheat bran (added with appropriate amount of water, boiled for 30 min and then filtrated to quit the solid residue), 20.00 g peptone, 1.50 g KH 2 PO 4 , 0.75 g MgSO 4 , natural pH˜6.3] for 6˜8 days at 25˜26° C. and 160 rpm in an orbital shaker. 
       Isolation, Purification and Analysis on the Glycosyl Hydrolase. 
       [0078]    The mycelium was harvested by filtration. After grinding with liquid nitrogen, 3˜5 volumes of 50 mM Tris-HCl cell lysis buffer (pH 8.0) was added and then the resultant was subjected to ultrasonic treatment for 5 min on ice (130 W, 10 seconds each time with a 10-second interval). The supernatant was collected after centrifugation (12000 rpm, 10 min), which was used as the crude enzyme solution for further isolation and purification. 
         [0079]    Protein with β-xylosidase activity was monitored by using the p-nitrophenyl-β-D-xylopyranoside (PNP-Xyl) as a specific chromogenic substrate. One unit of enzyme was defined as the amount of enzyme that is necessary to produce 1 nmol of p-nitrophenol by catalysis in 1 min at 50° C. and pH 5.0 with PNP-Xyl as the substrate. 
         [0080]    The above crude enzyme solution (80˜90 ml each time) was applied to a DEAE Sepharose FF anion exchange column (1.6 cm×20 cm) equilibrated with Tris-HCl buffer (50 mM, pH 8.0). Elution was performed with 50 mM Tris-HCl buffer (pH 8.0) with a gradient of 0, 0.1, 0.25, and 2.0 M NaCl (at a flow rate of 2 ml/min). Fractions of 0.1˜0.25 M NaCl eluent having enzyme activity were collected and added with 1 M (NH 4 ) 2 SO 4  for the subsequent chromatography. 
         [0081]    The fraction eluted in the above step was applied to a Phenyl Sepharose hydrophobic column (1.6 cm×20 cm) equilibrated with 50 mM Tris-HCl buffer (pH 8.0) containing 1 M (NH 4 ) 7 SO 4 . Elution was performed with Tris-HCl buffer (50 mM, pH8.0) having a linear gradient of 1.0˜0 M (NH 4 ) 2 SO 4  (at a flow rate of 2 ml/min). Fractions having enzymatic activity were collected and dialyzed with Tris-HCl buffer (50 mM, pH8.0). 
         [0082]    The dialyzed solution was applied to a DEAE Sepharose FF anion exchange column (1.6 cm×20 cm, equilibrated with 50 mM Tris-HCl buffer, pH 8.0). Elution was performed with a linear gradient of 0.1˜0.25 M NaCl in Tris-HCl buffer (50 mM, pH8.0) at a flow rate of 2 ml/min. Fractions with the highest enzyme activity were collected, concentrated and applied to a Sephacryl S200 HR molecular sieve chromatography column [1.6 cm×60 cm, equilibrated with Tris-HCl buffer (50 mM, pH 8.0) containing 0.1 M NaCl]. Elution was performed with 0.1 M NaCl in Tris-HCl buffer (50 mM, pH 8.0) at a flow rate of 0.5 ml/min. Fractions with the highest enzyme activity were collected. Finally the purified enzyme was obtained. 
         [0083]    Procedures for the purification described above are generalized as follows: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0084]    The results of each purification step for P1 are summarized in Table 1. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Total 
                 Total 
                 Specific 
                   
                   
               
               
                   
                 Volume 
                 protein 
                 activity 
                 activity 
                 Recovery 
                 Purification 
               
               
                 Purification step 
                 (ml) 
                 (mg) 
                 (U) 
                 (U/mg) 
                 ratio (%) 
                 fold 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Crude enzyme solution 
                 510 
                 527.8 
                 4099550.9 
                 7767.2 
                 100 
                 1 
               
               
                 DEAE Sepharose FF 
                 225 
                 91.8 
                 1384245.0 
                 15078.9 
                 33.77 
                 1.94 
               
               
                 Phenyl Sepharose 
                 120 
                 8.27 
                 1103753.3 
                 133464.7 
                 26.92 
                 17.18 
               
               
                 DEAE Sepharose FF 
                 25 
                 0.625 
                 426201.8 
                 681922.8 
                 10.40 
                 87.79 
               
               
                 Sephacryl S200 HR 
                 3 
                 0.048 
                 161373.8 
                 3361954.7 
                 3.94 
                 432.84 
               
               
                   
               
             
          
         
       
     
         [0085]    Two separate peaks [named LXYL-P1 (or P1) and LXYL-P2 (or P2), respectively] exhibiting β-xylosidase activity were obtained by elution in a linear gradient with the Phenyl Sepharose hydrophobic column. Both P1 and P2 could hydrolyze 7-xylosyl-10-deacetyltaxol (XDT) into 10-deacetyltaxol (DT) (as shown in  FIG. 1 ). In  FIG. 1 , penal A showed the enzymatic activity peaks obtained by chromatography; penal B showed the thin layer chromatography (TLC) of the substrate XDT conversion by enzymatically active samples P1 and P2, respectively. Within penal B, 1 was XDT control; 2 was DT control; 3 was XDT conversion by P1; and 4 was XDT conversion by P2. LC-MS/MS De novo sequencing results implied that P1 and P2 possessed the same amino acid residue sequence but are different in glycosylation forms. 
         [0086]    The reaction formula showing XDT being hydrolyzed into DT and xylose is illustrated as below: 
         [0000]    
       
                 
         
             
             
         
       
     
       Example 2 
     Specificity Test on Different Glycoside Substrates Hydrolysis by LXYL-P1 (or P1) Protein 
       [0087]    In addition to the β-xylosidase activity, especially the activity of hydrolyzing 7-xylosyltaxanes, the specificity of the LXYL-P1 (or P1) on other glycoside substrates was also tested by employing four chromogenic substrates: p-nitrophenyl-β-D-glucopyranoside (PNP-Glc), p-nitrophenyl-β-D-galactopyranoside (PNP-Gal), p-nitrophenyl-α-L-arabinopyrano side (PNP-Ara), and p-Nitrophenyl-β-D-xylopyranoside (PNP-Xyl, serving as a control). Each of the chromogenic substrates was prepared in 50 mM acetate buffer to obtain 5 mM solution (pH 5.0). 
         [0088]    To the purified P1 protein diluent (25 μl) obtained in example 1, 100 μl of each chromogenic substrate was added. The reaction was performed at 50° C. for 20 min and stopped with 2 ml saturated solution of sodium borate. Release of p-nitrophenol (absorbance value) was measured at 405 nm. The result showed that, P1 protein could hydrolyze PNP-Glc and PNP-Xyl, but not PNP-Gal and PNP-Ara. The results are shown in Table 2. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Relative activity 
               
               
                 Substrates 
                 OD 405  value 
                 (% control) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 p-nitrophenyl-β-D-xylopyranoside 
                 0.745 
                 100 
               
               
                 (PNP-Xyl) 
               
               
                 p-nitrophenyl-β-D-glucopyranoside 
                 1.615 
                 217 
               
               
                 (PNP-Glc) 
               
               
                 p-nitrophenyl-β-D-galactopyranoside 
                 0.000 
                 0 
               
               
                 (PNP-Gal) 
               
               
                 p-nitrophenyl-α-L-arabinopyranoside 
                 0.000 
                 0 
               
               
                 (PNP-Ara) 
               
               
                   
               
             
          
         
       
     
       Example 3 
     Cloning of the Encoding Gene (Lxyl-p1) of the Glycosyl Hydrolase LXYL-P1 
       [0089]    LXYL-P1 obtained in Example 1 was subjected to SDS-PAGE electrophoresis (see  FIG. 2 ), and the electrophoretic band with an apparent molecular weight of about 110 kDa after reduction treatment was recovered and subjected to LC-MS/MS analysis. The five oligopeptides with the highest peaks were selected and subjected to De novo sequencing and the amino acid residue sequences of the five oligopeptides were obtained as follows: 
         [0000]                                1.   LPWTWGK                       2.   QSGSLPLQHPQR                       3.   HWLAYEQETSR                       4.   DLPVGDSAVVTYPPR                       5.   TLTPLEALQK            
(Wherein I and L, K and Q are not distinguishable)
 
         [0090]    Bioinformatic approaches were applied to assess the relative locations of the five oligopeptides, and the order thereof on LXYL-P1 was determined to be: 3, 2, 5, 1, 4. Forward and reverse degenerate primers were designed as follows respectively according to oligopeptides 3 and 5: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 3F1: 
                 CTTGCGTACGAGCARGARAC 
               
               
                   
                   
               
               
                   
                 3F2: 
                 CACTGGCTTGCGTAYGARCA 
               
               
                   
                   
               
               
                   
                 3F3: 
                 CACTGGCTTGCNTAYG 
               
               
                   
                   
               
               
                   
                 5R1: 
                 AGCCTCCAGTGGCGTNAGNGT 
               
               
                   
                   
               
               
                   
                 5R2: 
                 CTGCAGAGCCTCCAGNGGNGT 
               
               
                   
                   
               
               
                   
                 5R3: 
                 TTCTGCAGAGCCTCNAGNGG 
               
             
          
         
       
     
         [0091]    The total RNA from the fungus M95.33 was used as the template and nest-PCR was performed by using the degenerate primers as described above. It was confirmed that the PCR products contained the coding sequences of the oligopeptides 3, 2 and 5. Then RACE technique was applied in elongation at both ends to obtain the cDNA fragment containing the coding region of the above-mentioned five oligopeptides. This fragment contains an open reading frame (ORF, or referred to as CDS, named Lxyl-p1) of 2412 by which encodes 803 amino acids. The cDNA sequence (SEQ ID NO: 3) and the amino acid sequence (SEQ ID NO: 2) encoded by this cDNA sequence are shown in the sequence list. The PCR amplification process is shown in  FIG. 8 . 
         [0092]    Specific primers were designed according to this cDNA sequence, and the structural gene sequence (G-Lxyl-p1) of LXYL-P1 was obtained by PCR amplification and Genome Walking technique, using the genomic DNA from the fungus M95.33 as the template. At the genomic level, the gene herein consists of 19 exons and 18 introns, with a length of 3608 by from the start codon ATG to the stop codon TGA. The nucleotide sequence (SEQ ID NO: 1) is shown in the sequence list. 
       Example 4 
     Construction of the Recombinant Plasmids and Screening of the Recombinant Yeasts 
       [0093]    SnaB I and Not I restriction enzyme sites were introduced by PCR to the 5′- and 3′-ends of the ORF (Lxyl-p1) of P1 coding region obtained in Example 3, respectively. After digestion with SnaB I/Not I, the resultant was then ligated to the  Pichia pastoris  expression vector pPIC9K (secreted expression vector) or pPIC3.5K (non-secretory expression vector), which was also digested with SnaB I/Not I, obtaining the recombinant expression plasmid pPIC9K-P1-2 or pPIC3.5K-P1-2. The recombinant plasmid was linearized by Sac I restriction enzyme and then transformed into the GS115 competent cells of  Pichia pastoris  by the electroporation transformation method. Meanwhile, the null vector pPIC9K or pPIC3.5K was also introduced into the GS115 competent cells of  Pichia pastoris  by the same method, respectively, as the control. The transformed yeast cells were spread on the MD plate [contains per liter: 20.00 g glucose, 13.40 g YNB (yeast nitrogen base without amino acids), 0.4 mg biotin, 15.00 g agar] and incubated at 28° C. for 2˜3 d. Single colony was picked up and inoculated on the YPD-Geneticin® resistant plate (contains per liter: 10.00 g yeast extract, 20.00 g peptone, 20.00 g glucose, 15.00 g agar, ≦4.00 g G418), and the cultivation was continued for another 2˜3 days to screen resistant colonies. The resistant colonies were subjected to colony PCR identification. Here are the examples of the transformants of pPIC9K and pPIC9K-P1-2 ( FIG. 3 ). 
         [0094]    PCR primers match with the AOXI sequences at the two sides of the cloning site in the pPIC9K vector, respectively: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 Forward: 
                 5′ GACTGGTTCCAATTGACAAGC 3′ 
               
               
                   
                   
               
               
                   
                 Reverse: 
                 5′ GGCAAATGGCATTCTGACATCC 3′ 
               
             
          
         
       
     
         [0095]    The strain transformed with the null vector pPIC9K gave an amplified fragment of 492 bp; while both the recombinant plasmid pPIC9K-P1-2 and its transformed strain gave an amplified fragment of 2910 bp. In  FIG. 3 , 1 showed the amplification result of the control recombinant yeast genome introduced with the null vector pPIC9K; 2 showed the amplification result of the recombinant yeast genome introduced with pPIC9K-P1-2; and 3 showed the amplification result of the control recombinant plasmid pPIC9K-P1-2. 
         [0096]    BMGY medium (contains per liter: 10.00 g yeast extract, 20.00 g peptone, 100 mM potassium phosphate buffer, pH 6.0, 10 ml glycerol) and BMMY medium (10 ml glycerol in BMGY medium was replaced with 10 ml methanol as the carbon source) were used as the seed culture and fermentation media respectively for the recombinant yeast. The resistant strain obtained by screening was inoculated into 10 ml seed culture medium and incubated at 30° C., 220 rpm for 18 h. The cultures were washed 2 times by centrifugation and the cell pellet was transferred into 50 ml fermentation medium. Cells were cultured at 30° C., 220 rpm, and 1% methanol was added every 24 h for induction of expression of the recombinant protein. Meanwhile the enzyme activity of the recombinant strain was detected regularly. The samples were washed 2 times with distilled water by centrifugation and the cell pellet was suspended in the same volume of distilled water. To 50 μl of the cell suspension, 100 μl of 5 mM PNP-Xyl was added and allowed to react for 20 min at 30˜55° C. It could be seen that the recombinant strain has the ability to hydrolyze the substrate PNP-Xyl while the control strain that was transformed with null vector did not show such ability (see  FIG. 4 ). In addition, no obvious enzymatic activity was detected in the supernatant of the fermentation broth of the recombinant strain, implying that the recombinant enzyme was mainly in the cells. 
       Example 5 
     Hydrolysis of 7-xylosyl-10-deacetyltaxol (XDT) by the Recombinant Yeast 
       [0097]    The recombinant yeast GS115-9K-P1-2 (transformant of the recombinant expression plasmid pPIC-9K-P1-2) obtained in example 4 was cultured and induced for 5 days in the manner of Example 4. Cells were centrifuged, harvested and washed, and then was, directly or after lyophilization, suspended with 50 mM acetate buffer or phosphate buffer (65 mg wet cells/ml or 16 mg dry cells/ml, pH 3.5˜7.5), and used as the hydrolytic reaction solution. To 20 ml of the cell reaction solution, 0.5 ml solution of 7-xylosyl-10-deacetyltaxol (XDT) was added with the final concentration of XDT being 0.625 mg/ml. The resultant was incubated in a water shaking bath for 12 h at 30˜55° C. 
         [0098]    Extraction was performed with ethyl acetate after the reaction was completed. TLC analysis showed that the substrate was completely transformed. HPLC [conditions: column: Agilent Eclipse XDB-C18 (4.6×150 mm, 5 μm), mobile phase: acetonitrile (38%˜52%), flow rate: 1 ml/min, column temperature: 28° C., detection wavelength: 230 nm] was used to analyze the contents of the XDT substrates and DT products in the extract, showing a conversion ratio of 98.80%. 
         [0099]    HPLC analysis on the XDT hydrolytic reaction result by the recombinant yeast is shown in  FIG. 5 , wherein A is before conversion, while B is after conversion. 
       Example 6 
     Hydrolysis of 7-xylosyltaxane Mixtures by the Recombinant Yeast 
       [0100]    The recombinant yeast GS115-3.5K-P1-2 (transformant of the recombinant expression plasmid pPIC3.5K-P1-2) obtained in Example 4 was applied in the following bioconversion reaction, wherein the substrates to be converted were 7-xylosyltaxane mixtures, the main components of which included 62.12% of 7-xylosyl-10-deacetyltaxol, 12.75% of 7-xylosyl-10-deacetylcephalomannine, 17.04% of 7-xylosyl-10-deacetyltaxol C, and 8.09% of other components. 
         [0101]    The method for culturing the recombinant strain was the same as in Example 5. 16 ml 7-xylosyltaxane mixtures (at a concentration of 100 mg/ml) were added to 200 ml recombinant strain reaction solution with the final concentration of the 7-xylosyltaxane mixtures being about 8 mg/ml (supersaturated). The recombinant yeast introduced with the null vector was taken as the negative control. The solution was mixed by magnetic stirring for 24 h at 30˜55° C. HPLC analysis was used to analyze the contents of substrates and products in the conversion system as the method in Example 5 after the reaction was completed ( FIG. 6 ), showing the following conversion ratios: 7-xylosyl-10-deacetyltaxol (XDT), 92.45%; 7-xylosyl-10-deacetylcephalomannine (XDC), 93.60%; and 7-xylosyl-10-deacetyltaxol C (XDTC), 92.00%. The yields of the three main products: 10-deacetyltaxol (DT): 3.27 mg/ml; 10-deacetylcephalomannine (DC): 0.74 mg/ml; and 10-deacetyltaxol C (DTC): 0.92 mg/ml. The total yield of the three main products was 4.93 mg/ml; while the control did not show any of the above activities ( FIG. 6 ). 
         [0102]    In  FIG. 6 , A showed the mixed substrates (control); B showed the recombinant yeast introduced with the null vector+mixed substrates (control); C showed the recombinant strain introduced with Lxyl-p1 gene+mixed substrates. 1 was 7-xylosyl-10-deacetylcephalomannine; 2 was 7-xylosyl-10-deacetyltaxol; 3 was 7-xylosyl-10-deacetyltaxol C; and 1′, 2′ and 3′ were the corresponding products of 7-xylosyltaxanes, respectively. 
       Example 7 
     Hydrolysis of 7-xylosyl-baccatin III (XDB) by the Recombinant Yeast 
       [0103]    The strain was the same as that in Example 6 and the substrate was 7-xylosyl-10-deacetylbaccatin III (XDB). 1.5 ml cell reaction solution contained 16 mg dry cells per millilitre and 8 mg XDB per millilitre. The mixture was incubated in a water shaking bath for 24 h at 30˜55° C. HPLC analysis results showed that the conversion ratio of XDB was 86.54% and the yield of the product, 10-deacetylbaccatin III (DB), was 5.57 mg/ml ( FIG. 7 ).