Patent Abstract:
a new human chitinase having an amino acid sequence as shown in fig . 1 or fig . 2 . modified forms of it having a similar chitin - hydrolyzing activity , and antigenic peptides representing one of its epitopes . recombinant production of the human chitinase by genetically engineered hosts or host cells . recombinant nucleic acid encoding it , and human chitinase - specific oligonucleotides . use for therapeutic or prophylactic treatment of humans against infection by chitin - containing pathogens , or for decomposing chitin , e . g . from chitin - based articles . antibodies binding to the human chitinase . diagnostic test kits comprising the human chitinase , its antigenic peptides , human chitinase antibodies , recombinant nucleic acid or oligonucleotides .

Detailed Description:
the fact that man is continuously exposed to chitin ( or chitin - containing organisms ) strongly suggests that man should also have the ability to degrade this material . a gradual , presumably lysosomal , accumulation of chitin would otherwise inevitably occur in life , e . g . in alveolar macrophages that are in continuous contact with chitin - containing organisms . however , such storage of chitin has never been noted . this prompted us to search for the occurrence of a chitinase activity in human macrophages . indeed , as is documented below , we were able to demonstrate that , in contrast to previous believes , macrophages can produce a chitinase similar in properties to enzyme encountered in other non - mammalian organisms ( 17 , 18 ). the enzyme is highly capable of hydrolyzing chitin and also shows other common characteristics of chitinases . based on the substrate initially used in the identification of the novel enzyme , i . e . 4 - methylumbelliferyl - chitotrioside , the human chitinase has been named chitotriosidase ( 17 ). a number of recent findings concerning chitotriosidase that were made at our laboratory are discussed . this information increases the insight in the features of this recently discovered enzyme . modest levels of chitotriosidase are detectable in lysosomes and specific granules of neutrophils . no chitotriosidase activity is demonstrable in erythrocytes , thrombocytes , lymphocytes and monocytes . we observed that exposure of neutrophils to lipopolysaccharide ( lps ) results in release of chitotriosidase . in healthy volunteers administration of gm - csf also leads to a temporary increase in plasma chitotriosidase levels , presumably caused by secretion of enzyme by neutrophils . the release of chitotriosidase mimicks that of lactoferrin . in isolated blood neutrophils no chitotriosidase mrna was detectable . this suggests that the enzyme is produced in precursors of these cells in the bone marrow . chitotriosidase can be massively produced and secreted by macrophages . during the differentiation of cultured monocytes to macrophages production of chitotriosidase is a late event : only after one week of cell culture , the first mrna and corresponding enzyme activity is detectable whilst other macrophage markers such as the tartrate resistant acid phosphatase are induced much earlier during the differentiation process . it appears that a particular kind of activation of macrophages , that spontaneously occurs during long - term culture of peripheral blood derived cells , is required for induction of chitotriosidase . isolated peritoneal macrophages of the rat do not produce chitotriosidase , not even after prolonged culture . it is conceivable that some types of differentiated tissue macrophages are no longer able to synthesize chitotriosidase . furthermore , not every trigger causing activation of macrophages may be compatible with chitotriosidase induction . we noted that activation of monocyte - derived macrophages with lipopolysaccharide ( lps ) did in fact reduce secretion of chitotriosidase . a potent trigger for chitotriosidase production by macrophages is apparently generated by lysosomal ( glyco ) lipid accumulation . it was noted that plasma chitotriosidase activities are elevated in a variety of lysosomal lipidoses , e . g . niemann - pick disease , krabbe disease , gm 1 gangliosidosis , and wolmann disease , although far less spectacular than in gaucher disease . interestingly , lysosomal storage disorders characterized by the accumulation of specific oligosaccharides or mucosaccharides are not accompanied by chitotriosidase elevations . it has become clear that the glucocerebrosidase deficiency in cells of gaucher disease patients is in itself not causing excessive chitotriosidase production . presymptomatic or asymptomatic gaucher patients do not show abnormal chitotriosidase levels . abnormal enzyme levels do correlate with clinical manifestation of gaucher disease , i . e . the occurrence of lipidloaden macrophages in tissues and bone marrow . it is currently felt that markedly elevated levels of chitotriosidase in plasma are a reflection of the presence of macrophages in a particular state of activation . increased enzyme levels have been noted in patients with inherited lysosomal lipidoses , in patients with visceral leishmaniasis , and patients with sarcoidosis . it is of interest to note that the leishmania parasite also resides in lysosomes of macrophages and possibly sheds glycolipid - like structures . the etiology of sarcoidosis is so far not known . the disease , that might be due to an infectious agent such as mycobacterium , involves immunological granuloma formation containing multinucleate giant cells with features of macrophages . chitotriosidase may prove to be a useful marker for other disease states in which pathological macrophages are involved . one attractive candidate is formed by atherosclerosis , that is characterized by the presence of cholesterol - loaden macrophages . moreover , we have noted elevated chitotriosidase levels in cerebral spine fluid of patients suffering from x - linked adrenoleukodystrophy and multiple sclerosis . it is believed that in both disorders activated brain macrophages ( microglial cells ) are an essential feature of the pathogenesis . clearly , chitotriosidase can be used as a diagnostic marker for onset of gaucher disease , and most likely other lysosomal lipidoses . furthermore , detection of elevated plasma enzyme levels may be useful in the diagnosis of sarcoidosis and detection of elevated enzyme levels in cerebral spine fluid in the case of some neurodegenerative disorders . moreover , the correction in enzyme levels upon therapeutic intervention may be an important tool to monitor the efficacy of treatment and could serve as a guideline for optimalization of therapy . in order to use the human chitinase ( chitotriosidase ) as a ( pharmaceutical ) agent against chitin - containing organisms in vivo , a number of conditions have to be fulfilled . an important issue is the tolerance of the body for chitotriosidase . as mentioned above , the human body is not believed to contain endogenous chitin . in analogy to lysozyme , a chitinase activity should therefore be harmless for the body . since chitotriosidase is an endogenous protein that occurs in the circulation , it appears unlikely that an immune response is elicited by additional administration of the enzyme to man . large concentrations of the chitotriosidase can be encountered in the circulation of patients with gaucher disease , which is a recessively inherited lysosomal storage disorder characterized by the massive occurrence of glucosylceramide loaden macrophages in various tissues ( 17 ). the excessive amounts of the enzyme in plasma of gaucher patients are without any apparent harmful consequences . this finding suggests that excessive amounts of chitotriosidase in the circulation are well tolerated by man , an important prerequisite for its potential use to combat chitin - containing pathogens . in order to be useful as an agent against chitin - containing pathogens chitotriosidase has furthermore to be available in large quantities in a uniform state . there are no ubiquitous , natural sources for the isolation of the human chitinase . the mounts of enzyme in urine and placentas are low . this led us to attempt to isolate cdna encoding chitotriosidase . due to the specific expression of the chitotriosidase gene in macrophages , all tested cdna libraries from other cell types were found to be negative for chitotriosidase cdna . however , a constructed cdna library from mrna of long - term cultured macrophages that secreted massive amounts of chitotriosidase activity proved to be extremely rich in cdnas encoding chitotriosidase , ( 0 . 1 % of total cdna ). two distinct cdnas were in this manner identified and cloned . the occurrence of two distinct cdna species is due to alternative splicing of rna , resulting in two distinct mrna species which are both functional . expression of the two cdnas in cos cells results in synthesis and secretion of two discrete chitotriosidase proteins with apparent molecular weights of 39 and 50 kda with polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate . both recombinant produced chitotriosidase isozymes , named chitozyme 50 and chitozyme 39 , were enzymatically active . further characterization of the recombinant chitotriosidase isozymes indicated that their specific activity , i . e . enzymatic activity per amount of antigen , was identical to that of chitotriosidase isolated from tissue or present in plasma . as described in the section ‘ experimental data ’ in detail , the two chitotriosidase proteins are largely identical , being only distinct in their c - terminal portions . the isozymes contain the highly conserved , presumed catalytic center region of chitinases belonging to class 18 of glycosylhydrolases ( 19 ). the nucleotide sequences of the cloned cdnas predict that both chitotriosidase proteins lack n - linked glycans . indeed , the presence of any glycans was not demonstrable for the 39 kda form . the presence of o - linked glycosylation cannot be excluded for the 50 kda form . the findings suggest that large scale recombinant production of both forms of human chitotriosidase using conventional techniques should be feasible . moreover , it seems likely that not only production of the human enzyme in eukaryotic cells , but even in prokaryotes might be possible , since highly homologous proteins are endogenously produced by some of these organisms , e . g . serratia marcescens . a procedure for the purification of chitotriosidase has been successfully developed ( 18 ; and below ) it therefore will be possible to obtain large amounts of both recombinant human chitotriosidases in a pure and uniform state suitable for administration to man . the 39 kda chitozyme is not a glycosylated protein , so its production in prokaryotic cells should certainly be feasible . bacteria which produce and secrete highly homologous chitinases should in principle be able to secrete correctly folded human chitotriosidase in their exoplasmic space , provided that a correct leader sequence is used . alternatively , it could be considered to use yeast cells for the production of recombinant chitotriosidase , at least the 39 kda chitozyme . it can so far not be excluded , however , that also 50 kda chitotriosidase can be produced , not only in higher eukaryotes , but also in lower eukaryotes or even in prokaryotes . production of the chitozymes via conventional technology in insect cells , plant cells , or vertebrate cells should be possible . finally , transgenic animals could be envisioned as producers of large quantities of chitozymes in their milk for the applications described above . it was observed that chitozyme when added to cow milk was completely stable for several hours at 37 ° c . another constraint in the application of an enzyme as therapeutic agent is formed by its ability to survive and to be functional in the body . attention has therefore been focussed to the properties of chitotriosidase . both forms of recombinant chitotriosidase ( chitozymes 39 and 50 ) prove to be extremely stable against a variety of proteases . successful proteolytic cleavage is only accomplished after denaturation of the enzyme , e . g . after heating in the presence of sodium dodecylsulphate . prolonged incubation of serum or plasma at 37 ° c . does not result in detectable loss of enzyme activity , suggesting that the enzyme is insensitive to serum proteases . in analogy , chitotriosidase is stable at 37 ° c . in macrophage - conditioned medium that contains large quantities of various other secreted lytic enzymes . further analysis revealed that the chitotriosidase isozymes are comparably stable and enzymatically active in the ph range of from 3 to 8 . moreover the enzyme is completely stable at 50 ° c . and enzyme activity is still recovered after spotting an enzyme solution on filter paper followed by storage for several days at room temperature . no loss of enzyme activity occurs upon storage at − 20 or − 70 ° c ., and repeated cycles of freezing and thawing . all these observations suggest that the chitotriosidase isozymes are truly stable enzymes , intrinsically highly resistant against denaturation and showing the potential to be functional in various environments . a prerequisite for the intravenous application of the chitinase is insight in its clearance . in the blood stream the most predominant isozyme is the 50 kda protein . in tissue predominantly a 39 kda isozyme is encountered . this appears to be formed by uptake of 50 kda protein followed by proteolytic cleavage to a 39 kda form that is remarkably stable in the lysosomal environment . experiments in rats suggest that the half life of recombinant 50 kda chitotriosidase in the circulation is somewhat longer than that of the 39 kda enzyme . clearance is not a very rapid process as monitored by the disappearance of activity of human chitotriosidase in the blood stream of intravenously injected rats , the half life being about one hour . only minor amounts of chitotriosidase are daily excreted into the urine . it is conceivable that some enzyme is efficiently recaptured by proximal tube epithelial cells since kidney is found to be extremely rich in ‘ lysosomally processed ’ 39 kda enzyme . the observations so far suggest that intravenous administration can lead to a high level of human chitinase activity in the circulation for a prolonged period of time , allowing enzyme to reach various tissue locations . purified chitotriosidases are well able to hydrolyse chitin and artificial chitin - like substrates such as pnp - chitotrioside , pnp - chitobioside , 4mu - chitotrioside and 4mu - chitobioside . moreover , it was noted that addition of chitotriosidase to a fungus ( mucor species ) inhibited growth . these findings are in line with the expectations based on the high level of homology of chitotriosidase with chitinases from other species . summarizing , both chitotriosidase enzymes have properties that are advantageous with respect to their use as therapeutic agent . both forms of the enzyme can be relatively easy produced via conventional recombinant techniques . the enzymes are extremely stable and capable of enzymatic activity under various conditions . the recombinant chitozyme 39 and chitozyme 50 , and tissue chitotriosidase are not immediately cleared from the circulation , at least in the rat model , and could in principle be distributed to various tissue locations . the above findings concerning chitotriosidase have prompted us to claim here that natural and recombinant chitotriosidases ( chitozymes ) are attractive agents for use in intervention of infectious diseases due to organisms that contain chitin or related structures that are susceptible to hydrolysis by the enzyme . the two recombinant chitotriosidases , chitozyme 50 and chitozyme 39 , have so far always been found to be identical in enzymatic properties , i . e . specific activity , ph dependence and stability . both chitozymes might be used as agents against various pathogens containing chitin ( see table 1 ). infections with chitin - containing pathogens occur at various locations in the body . due to their intrinsic properties chitozymes can be considered to be suitable for application at various body locations . topical application can be considered for the treatment of infections of superficial mycoses that occur at the skin . infections in the eye , reproductive tract and intestinal tract by chitin - containing organisms could also be treated by local administration . relevant infections of the pulmonary system could be treated by use of a spray containing enzyme . oral administration can be considered for the use against infectious chitin - containing organisms in the mouth and gastrointestinal tract . finally , as indicated in the previous section , intravenous administration can be considered for intervening with pathogens present in the blood stream and tissues , either interor intra - cellularly . additional research should reveal whether more specific targetting is possible by the use of specific chitozyme isoforms . this invention furthermore embraces several variants and modifications , such as especially the following possibilities . it is well documented that both in plants and fish chitinases play an important role in resistance against fungal infections . in plants , chitinases act synergistically with β - 1 , 3glucanases since the cell walls of fungi are composed of a mixture of chitin and βglucan fibrils ( 15 ). at present it is believed that man is not capable of producing a chitinase nor a β - glucanase . however , it was noted that long - term cultured macrophages are not only able to secrete a chitinolytic enzyme but also an enzyme active against dye - labeled β - glucan . we therefore propose that analogous to the situation in plants a mixture of human chitinase and β - glucanase could be a more powerful anti - fungal agent than one of these enzymes alone . isolation of the β - glucanase produced by long - term cultured macrophages and subsequent cloning of corresponding cdna , should result in the availability of recombinant human β - glucanase for this purpose . increasing insight in the 3 - dimensional structure of chitotriosidase and the function of its several domains will allow engineering of modified forms of the enzyme for specific applications . for example , production of recombinant enzyme lacking domains that are not essential for catalytic activity and specificity might lead to a much smaller core protein that is still active and meanwhile more easily penetrates specific locations in the body . the currently available and rapidly extending knowledge about the structure of family 18 and family 19 glycosylhydrolases suggests that engineering of modified forms of chitinases is a realistic option . in addition to therapeutical applications , the invention also embraces prophylactic applications . we observed that plasma chitotriosidase activity tends to be higher with increasing age , being on the average several - fold higher in plasma of individuals older than 60 years of age than children . moreover , we found that 1 in about every 15 individuals is unable to produce active chitotriosidase ( see ref . 17 ). these individuals are deficient in enzyme activity in plasma and urine , and in leukocytes and long - term cultured macrophages derived from peripheral blood monocytes . chitotriosidase deficiency occurs with a similar frequency among patients with gaucher disease as normal subjects . the clinical course of the disease is identical in patients that are deficient and those with several thousand - fold elevated plasma enzyme levels . this indicates that the chitotriosidase elevation is a hallmark of , but not a prerequisite for , clinical manifestation of gaucher disease . it was noted by us that chitotriosidase deficiency is an inherited trait . strongly reduced levels of chitotriosidase mrna as well as protein were observed for long - term cultured macro - phages obtained from peripheral blood monocytes of individuals deficient in chitotriosidase . the fact that the residual chitotriosidase protein shows a normal molecular mass and lacks enzymatic activity suggests that at least in these cases the underlying defect is some mutation in the chitotriosidase gene . metabolic labeling and northern blot analysis suggest that this mutation results in reduced synthesis of a catalytically impaired chitotriosidase protein . it cannot be excluded that a deficiency in chitotriosidase may be associated with some disadvantage . for example , the resistance against chitin - containing pathogens could be reduced and lysosomal degradation of chitin in phagocytes could be impaired , resulting in abnormal behaviour of the cells . further research is required to establish whether a chitotriosidase deficiency is indeed associated with some risks . if this proofs to be the case , prophylactic administration of human chitotriosidase to deficient individuals could be considered . other situations that may lead to a functional deficiency in chitotriosidase activity are immunodeficient states . we noted for example that in patients with acquired immunodeficiency due to a hiv infection plasma chitotriosidase levels are on the average reduced . furthermore it was noted that corticosteroid treatment of patients with sarcoidosis resulted in a rapid reduction of chitotriosidase activity . apparently the presence of activated macrophages is an important factor in maintaining normal chitotriosidase levels in the circulation . supplementation with recombinant chitotriosidase may be considered in immuno - incompetent individuals that are at increased risk for infections with chitin - containing pathogens . local application of recombinant chitotriosidase could be also considered in the case of wounds to reduce the risk of infections with fungi . the availability of a human chitinase could be also exploited as a tool to degrade injected or implanted chitinbased structures for medical purposes . for example , drugs could be incorporated in chitin based capsules (‘ chitosomes ’). the concomitant presence of well defined amounts of human chitinase in the capsule could ensure a controlled release of drugs . a slow but gradual release of drug could particularly be envisioned when it is trapped in a chitin matrix . the use of the human enzyme in such a system would result in ultimate destruction of the chitin - based capsule and not elicit an immunological response . the drugs used in such a system could vary from small compounds to proteins and dna fragments for the purpose of enzyme and gene therapy . chitin ( or analogues ) is already employed as a carrier for drugs ( 20 ). another , related , application is the use of recombinant chitotriosidase for the swift degradation of implants that contain chitin as a structural component . this would be useful in the case of implants that only temporarily have to fulfil a function and can be conveniently ‘ dissolved ’ by administration of recombinant chitotriosidase . recombinant chitotriosidase can be also used ex vivo as a fungicidal compound . for example , as a preventive measure recombinant chitotriosidase ( or a cocktail with β - 1 , 3 - glucanase ) could be added to culture medium of human cells that preferably need to be cultured in the absence of antibiotics and have to be re - administered to the human body . examples in this connection may be the ex vivo culture of cells for the purpose of gene therapy and the ex vivo culture of keratinocytes to be used in connection with wound healing . finally , recombinant human chitotriosidase ( or a cocktail with β - 1 , 3 - glucanase ) may be used as an additive in tooth paste and body lotions in order to prevent fungal infections . the invention will now be illustrated by the following examples which merely serve to exemplify the invention and are not intended to limit the scope of the invention . in order to clone cdna encoding human chitotriosidase the following strategy was used . chitotriosidase was purified from spleen of a type 1 gaucher disease patient since this organ is extremely rich in chitotriosidase activity ( 18 ). the n - terminal amino acid sequence of chitotriosidase was determined and this information was used for cloning chitotriosidase cdna . firstly , the established n - terminal amino acid sequence of chitotriosidase ( 18 ) was used to design a degenerate sense oligonucleotide : 5 ′- tgytayttyacnaaytgggc - 3 ′( seq id no : 1 ). secondly , a degenerate anti - sense nucleotide was designed based on the highly conserved domain among chitinases that is presumed to be an essential part of the catalytic center : 5 ′- ccartciarrtyiaciccrtcraa - 3 ′ ( seq id no : 2 ). these oligonucleotides were used to amplify a dna fragment by rt - pcr . for this purpose , total rna had been isolated from long - term cultured macrophages that secreted large amounts of chitotriosidase activity . first strand cdna synthesis was performed using superscript tm rnase h , reverse transcriptase and oligo dt . after alkaline hydrolysis , the cdna was precipitated with ethanol and used as template . pcr was performed using standard conditions . the dna fragment obtained by rt - pcr was of the expected size ( on the basis of homology with members of the chitinase family ). the fragment was purified , treated with t4 dna polymerase and cloned into the hindii site of the plasmid vector puc19 . determination of its sequence using the dideoxy - nucleotide chain termination method revealed that the fragment was in complete accordance with the known n - terminal amino acid sequence of purified human chitotriosidase , allowing its use as a probe to identify a full length chitotriosidase cdna . a cdna library was prepared using total rna from cultured macrophages . double stranded macrophage cdna was prepared from rna using the superscript choice system cdna synthesis kit from gibco - brl . double stranded cdna was ligated to an excess of non - palindromic bstx1 linkers and subsequently size fractionated on a low melting type agarose gel . the cdna exceeding 500 bp was purified and ligated into bstx 1 sites of the vector pcdnal ( invitrogen ). the ligation mixture was electroporated into escherichia coli strain mc106 / p3 to obtain a macrophage cdna library . the cdna library was screened by colony hybridization using the partial chitotriosidase cdna probe that had been radiolabelled by the random priming method . hybridization to the probe was carried out for 4 h in 1 mm edta , 0 . 5 m sodium hydrogen phosphate buffer ( ph 7 . 2 ) containing 7 % ( w / v ) sodium dodecylsulphate at 65 ° c . next , the filters were washed twice in 150 mm sodium chloride , 15 mm sodium citrate ( ph 7 . 0 ) containing 0 . 1 % ( w / v ) sodium dodecylsulphate , and subjected to autoradiography . about 0 . 1 % of the colonies were positive upon hybridization with the partial chitotriosidase cdna clone . about 20 clones were sequenced as described above . two distinct , full length chitotriosidase cdnas were in this manner identified . the two clones are designated as chi . 50 and chi . 39 . the nucleotide sequence ( seq id no : 3 ) of the cdna clone chi . 50 shows an open reading frame starting with an atg at position 13 and ending with a tga codon at position 1410 ( see fig1 ). the open reading frame encodes a protein with a characteristic n - terminal er signal peptide , immediately followed by the n - terminal sequence established for the chitotriosidase protein . the cdna sequence does not indicate the presence of potential n - linked glycosylation sites , which is consistent with the absence of n - linked glycans in isolated chitotriosidase . the predicted protein , after removal of the signal sequence , has a length of 445 amino acids and a calculated molecular mass of 49 kda . metabolic labelling experiments with cultured macrophages revealed that these cells predominantly synthesize and secrete a chitotriosidase protein with apparent molecular mass of 50 kda with polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate at reducing conditions . the predicted c - terminal part of 50 kda human chitotriosidase is rich in serine residues of which theoretically some might be o - linked glycosylated . the occurrence of this type of glycans in 50 kda human chitotriosidase has so far not been excluded or confirmed . the nucleotide sequence ( seq id no : 5 ) of the cdna clone chi . 39 shows an open reading frame that encodes an almost identical chitotriosidase protein with a total of 387 amino acids ( see fig2 ). after removal of the hydrophobic leader , the predicted protein for chi . 39 cdna has a length of 366 amino acids and expected molecular mass of 39 kda . the signal peptide and the first 384 amino acids are identical to those in the chitotriosidase protein encoded by the chi . 50 cdna . only the 3 most c - terminal amino acids in the predicted 39 kda chitotriosidase are distinct from those in the protein predicted for chi . 50 cdna . comparison of the nucleotide sequences of both cdnas suggests that an additional sequence of nucleotides is inserted in the chi . 39 cdna . again , no n - linked glycosylation is predicted for the chi . 39 cdna encoded chitotriosidase . the relationship between various forms of chitotriosidase is shown in fig3 . the composition of the two cloned chitotriosidase cdnas strongly suggested that alternative splicing causes the formation of two distinct mrnas . the chi . 39 cdna contains an additional exon of the chitotriosidase gene as compared to the chi . 50 cdna , as was experimentally verified . genomic chitotriosidase dna was cloned and partially sequenced . the sequence shows indeed intron - exon transitions that are consistent with the assumption that the two distinct cdna clones ( representing different mrna species ) are the result of alternative splicing of chitotriosidase rna . metabolic labelling experiments with cultured macrophages showed that concomitantly large amounts of 50 kda chitotriosidase protein and very small amounts of a 39 kda protein were initially synthesized . in accordance with these findings , rnase protection analysis revealed the concomitant presence of chi . 50 rna and minor amounts of chi . 39 rna in macrophages . it was furthermore noted that secreted 50 kda chitotriosidase can be proteolytically processed to a 38 - 39 kda protein after uptake by macrophages . it may be that some newly synthesized chitotriosidase is not secreted , but directly routed to the lysosomal apparatus where it is further proteolytically processed . from spleen of gaucher disease patients at least two isoforms of chitotriosidase can be isolated . the apparent molecular masses are 50 and 39 kda with polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate . the exact molecular mass for 39 kda chitotriosidase isolated from tissue was determined using electron spray mass spectrometry . this analysis indicates that the 39 kda tissue enzyme ( that has the normal n - terminus ) has undergone c - terminal proteolytic processing . it should be noted that proteolytic processing of the 39 kda precursor ( removal of four c - terminal amino acids ) as well as the 50 kda precursor ( removal of 83 c - terminal amino acids ) would both yield the tissue enzyme . a search of the embl and genbank databases revealed significant homology between the two human chitotriosidases and a group of chitinases and related proteins from different species . all the homologous proteins belong to the so called ‘ chitinase protein family ’ ( 18 , 19 ). the strongest homology is noted for a region that is presumed to be an essential element of the catalytic center in chitinases ( see fig4 ). additional homologous regions with members of the chitinase family were identified . in fig1 the amino acids in 39 kda chitotriosidase that are identical to those in at least 6 out of 9 members of the chitinase protein family are indicated by bold characters . the predicted c - terminal part of 50 kda human chitotriosidase shows only homology with two chitinases from manduca sexta and brugia malayi , respectively . in the case of the latter enzyme o - linked glycosylation has been reported ( 12 ). cos - 1 cells were transiently transfected with the two chitotriosidase cdnas by the deae - dextran method as described previously ( 21 ). the production of chitotriosidase was monitored by measurement of secreted enzyme activity . the chitotriosidase activity in culture medium was measured using the fluorogenic substrate 4 - methylumbelliferyl - chitotrioside as described before . the medium of cos cells , transfected with either chi . 50 or chi . 39 cdna , contained 7 days after transfection large amounts of chitotriosidase activity ( 5 - 20 mu / ml ). no activity was detected in the case of mock transfected cos cells or cells transfected with the same cdna inserted in the anti - sense orientation . the chitotriosidase produced by cos cells was analysed by immunotitration with a rabbit antiserum against human chitotriosidase . this antiserum is capable of inhibiting human chitotriosidase in its enzymatic activity . fig5 shows that chitotriosidase is inactivated by the antiserum in an identical manner to isolated splenic chitotriosidase . this finding suggests that the enzymatic activity per amount of antigen is similar in the case of the two recombinant chitotriosidases and the splenic enzyme . no differences were noted in ph - profile , stability , km for 4 - methylumbelliferyl - chitotrioside and 4 - methylumbelliferyl - chitobioside when both recombinant enzymes (‘ 50 and 39 chitozymes ’) were compared with splenic chitotriosidase . metabolic labelling experiments revealed that the cos cells transfected with the chi . 50 cdna and chi . 39 cdna , respectively , produced chitotriosidase proteins with the expected molecular masses of 50 and 39 kda , respectively . previously we developed a procedure for the purification of 39 kda and 50 kda chitotriosidase from gaucher disease spleen ( 18 ). the procedure renders pure 39 kda chitotriosidase and partially pure 50 kda enzyme . briefly , a detergent - free extract is applied to a polybuffer exchange column ( pbe 94 , pharmacia biotech inc . ); the column is equilibrated and eluted with 25 mm tris buffer ( ph 8 . 5 ). breakthrough fractions with highest chitotriosidase activity are pooled and concentrated by ultrafiltration . this pool is applied to a sephadex c - 1000 column and eluted with 25 mm tris buffer ( ph 8 . 0 ). peak fractions containing enzyme activity are pooled , concentrated and subjected to preparative isoelectric focussing using ultrodex ( pharmacia ) containing 0 . 5 % ( v / v ) triton x - 100 and 0 . 1 % ( w / v ) ampholytes ( servalyte 4 - 9 , serva ). after focussing overnight at 10 ° c . and 400 v , the gel is fractionated and extracted with water . fractions with pi 8 . 0 contain pure chitotriosidase with apparent molecular mass of 39 kda with polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate . fractions with pi around 7 . 2 contain 50 kda chitotriosidase contaminated with some other proteins . complete purification of the impure 50 kda chitotriosidase can be accomplished by incubation of enzyme preparation with chitin particles in citrate / phosphate buffer ( ph 5 . 2 ) at 4 ° c ., followed by elution at room temperature in the presence of 4 m sodium chloride in the same buffer . the contaminants are not bound or completely removed by washing of the chitin particles with ice - cold citrate buffer containing 0 . 1 m sodium chloride and 0 . 5 % ( v / v ) triton x - 100 . the same isolation procedure is applicable for isolation of recombinant chitotriosidases ( chitozymes ) from culture medium cells transfected with chitotriosidase cdnas . the specific activity of purified 39 and 50 kda recombinant chitotriosidase is identical to purified tissue enzyme , i . e . from 6 to 6 . 5 mmol substrate hydrolysis / mg protein x hour using the artificial substrate 4 - methylumbelliferyl - chitotrioside at conditions previously described . purified 50 kda and 39 kda tissue chitotriosidases , and 50 kda and 39 kda chitozymes produced by recombinant dna technology , are able to hydrolyse 4 - methylumbelliferyl - chitotrioside and 4 - methylumbelliferyl - chitobioside , the ratio of chitobioside activity to chitotrioside activity being about 0 . 7 . furthermore , p - nitrophenyl - chitotrioside and p - nitrophenyl - chitobioside are also efficiently hydrolyzed . chitin azure ( sigma ) suspended in citrate / phosphate buffer ( ph 5 . 2 ) at a final concentration of 10 mg / ml was used to monitor chitinase activity . chitin degradation was detected spectrophotometrically at 550 nm by determination of release of soluble azure ( 18 ). chitinase from serratia marcescens ( sigma ) was used as control . when related to the hydrolysis of 4 - methylumbelliferyl - chitotrioside , the chitinase activity of human chitotriosidase was comparable to that of the bacterial chitinase . see for example ref . 18 . no significant activity of human chitotriosidase towards a cell wall suspension of micrococcus lysodeikticus was detectable , suggesting that the enzymes lack lysozyme activity . to test whether human chitotriosidase can exert an anti - fungal action , a chitinous fungus ( mucor mucedo ) was grown on plates ( containing malt extract , peptone , glucose and agar ) under a cellophane membrane in order to keep the hyphae flat against the agar surface ( see ref . 16 ). individual sectors were cut out and mounted on microscope slides . purified chitozyme 50 and chitozyme 39 were dialysed against 0 . 15 m sodium chloride . samples of enzyme - containing solutions , and 0 . 15 m nacl were pipetted on the hyphal tips . microscopical analysis revealed that application of enzyme resulted in immediate cessation of hyphal growth , followed by a distorted morphological appearance . application of saline had no effect . negative effects on hyphal growth were detectable using chitozyme solutions with a concentration of enzyme as little as 0 . 005 mg / ml . fig1 . nucleotide sequence ( seq id no : 3 ) of chi . 50 cdna clone and predicted amino acid sequence ( seq id no : 4 ) of corresponding protein . the hydrophobic leader ( amino acids 1 - 21 ) is underlined . amino acids in chitotriosidase that are identical to those in at least 6 out of 9 members of the chitinase family are depicted in bold characters . the 9 members of the chitinase family used are listed in the legend of fig4 with the exception of the chitinases from autographa californica and nicotiana tabacum . fig2 . nucleotide sequence ( seq id no : 5 ) of chi . 39 cdna clone and predicted amino acid sequence ( seq id no : 6 ) of corresponding protein . fig3 . schematic overview of various chitotriosidase isozymes produced in macrophages . due to alternative splicing , two distinct mrnas are generated that are translated into chitotriosidase proteins with apparent molecular masses of 39 and 50 kda . both forms are predominantly secreted . however , some enzyme may be directly routed to lysosomes or be endocytosed and reach this compartment . in the lysosome , further proteolytic processing of the c - terminus may occur to a form of about 38 - 39 kda . both precursors ( 39 and 50 kda ) can in this way be processed to an identical lysosomal form . it cannot be excluded that the c - terminal part of 50 kda chitotriosidase contains o - linked glycans . the 39 kda precursor and the lysosomally processed chitotriosidase are free of glycans . fig4 . alignment of putative active site regions in some members of the chitinase protein family . the proteins are : human chitotriosidase ( seq id no : 7 ); a chitinase from the virus autographa californica ( genbank l22858 ( seq id no : 8 )); a chitinase from the tobacco hornworm manduca sexta ( genbank u02270 ( seq id no : 7 )); an endochitinase from the nematode brugia malayi ( genbank m73689 ( seq id no : 9 )); a human oviductal glycoprotein ( genbank u09550 ( seq id no : 10 )); hcgp - 39 , a human glycoprotein produced by chondrocytes and synovial cells ( genbank m80927 ( seq id no : 11 )); ym - 1 , a secretory protein of activated mouse macrophages ( pir s27879 ( seq id no : 12 )); a chitinase from the fungus aphanocladium album ( swissprot p32470 ( seq id no : 13 )); a chitinase from the filamentous fungus trichoderma harzianum ( genbank l14614 ( seq id no : 14 )); chitinase a 1 from the prokaryote bacillus circulans ( swissprot p20533 ( seq id no : 15 )); and a class v chitinase from the plant nicotiana tabacum ( genbank x77110 ( seq id no : 16 )). residues identical to chitotriosidase are indicated by the inverted characters . the proteins hcgp - 39 and ym - 1 are supposed to be not chitinolytic . fig5 . immunotitration of 39 and 50 kda chitotriosidase purified from spleen and that of 39 and 50 kda enzyme produced by transfected cos cells . preparations containing either purified 39 kda splenic chitotriosidase ( ), or 50 kda chitozyme produced by cos cells transfected with chi . 50 cdna ( ), or 39 kda chitozyme produced by cos cells transfected with chi . 39 cdna were incubated for 1 hour at room temperature in phosphate buffered saline with different amounts of rabbit ( anti - human splenic chitotriosidase ) antiserum . binding of antibody to chitotriosidase results in loss of enzymatic activity . residual enzyme activity upon incubation of enzyme preparations with antiserum was determined by measurement of activity towards the substrate 4 - methylumbelliferyl - chitotrioside ( 18 ). the similarity in the immunotitration curves of various chitotriosidases indicates that the enzymes are identical in enzymatic activity per amount of antigen . 1 . immunology ( 3rd ed ; eds roitt , i ., brostoff , j ., male , d .) 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( 1994 ), structure 2 , 1169 - 1189 . crystal structure of a bacterial chitinase at 2 . 3 angstrom resolution . 9 . wansborough - jones , m . n ., wright , s . g ., mcmanus , t . j ., infectious , tropical and parasitic diseases ( chapter 12 ) in : textbook of medicine ( souhami , r . l ., moxham , j ., eds ) ( 1990 ), churchill livingstone , london 10 . shahabuddin , m ., kaslow , d . c . ( 1994 ), exp . parasitol . 79 , 85 - 88 . plasmodium : parasite chitinase and its role in malaria transmission . 11 . nussenzweig , r . s ., long , c . a . ( 1994 ), science 265 , 1381 - 1383 . malaria vaccines : multiple targets . 12 . fuhrman , j . a ., lane , w . s ., smith , r . f ., piessens , w . f ., perler , f . b . ( 1992 ), proc . natl . acad . sci . usa 89 , 1548 - 1552 . transmission - blocking antibodies recognize microfilarial chitinase in brugian lymphatic filariasis . 13 . raghavan , n ., freedman , d . o ., fitzgerald , p . c ., unnasch , t . r ., ottesen , e . a ., nutman , t . b . ( 1994 ), infection and immunity 62 , 1901 - 1908 . cloning and characterization of a potentially protective chitinase - like recombinant antigen from wucheria bancrofti . 14 . sahai , a . s ., manochoa , m . s . ( 1993 ), fems microbiology reviews 11 , 317 - 338 . chitinases of fungi and plants : their involvement in morphogenesis and host - parasite interaction . 15 . shapira , r ., ordentlich , a ., chet , i ., oppenheim , a . b . ( 1989 ), phytopathology 79 , 1246 - 1249 . control of plant diseases by chitinase expressed from cloned dna in escherichia coli . 16 . manson , f . d . c ., fletcher , t . c ., gooday , g . w . ( 1992 ), j . fish biology 40 , 919 - 927 . localization of chitinolytic enzymes in blood of turbot , scophtahalmus maximus , and their possible roles in defence . 17 . hollak , c . e . m ., van weely , s ., van oers , m . h . j ., aerts , j . m . f . g . ( 1994 ), j . clin . invest . 93 , 1288 - 1292 . marked elevation of plasma chitotriosidase activity . a novel hallmark of gaucher disease . 18 . renkema , g . h ., boot , r . g ., muijsers , a . o ., donker - koopman , w . e ., aerts , j . m . f . g . ( 1995 ), j . biol . chem . 270 , 2198 - 2202 . purification and characterization of human chitotriosidase , a novel member of the chitinase family of proteins . 19 . hakala , b . e ., white , c ., reclies , a . d . ( 1993 ), j . biol . chem . 268 , 25083 - 25810 . human cartillage gp - 39 , a major secretory product of articular chondrocytes and synovial cells , is a mammalian member of the chitinase protein family . 20 . miyazaki , s ., ishii , k ., nadai , t . ( 1981 ), chem . pharm . bulletin 29 , 3067 - 3069 . the use of chitin and chitosan as drug carrier . 21 . lopata , m . a ., cleveland , d . w ., sollner - webb , b . ( 1984 ), nucleic acid res . 12 , 5701 - 5707 . pro trp gly ser ala ala lys leu val cys tyr phe thr asn trp ala gln tyr arg gln gly glu ala arg phe leu pro lys asp leu asp pro ser leu cys thr his leu ile tyr ala phe ala gly met thr asn his gly gly trp asn phe gly thr gln lys phe thr asp met val ala thr gln gly ser pro ala val asp lys glu arg phe thr thr leu val gln asp leu ala asn ala phe gln gln glu ala gln thr ser gly lys glu arg leu leu leu ser ala ala val pro ala gly gln thr tyr val asp ala gly tyr glu val asp lys ile ala gln asn leu asp phe val asn leu met ala tyr asp phe his gly ser trp glu lys val thr gly his asn ser pro leu tyr lys arg gln glu glu ser gly ala ala ala ser leu asn val asp ala ala val gln gln trp leu gln lys gly thr pro ala ser lys leu ile leu gly met pro thr tyr gly arg ser phe thr glu val cys ser trp lys gly ala thr lys gln arg ile gln asp gln lys val pro tyr ile phe arg asp asn gln trp val gly phe asp asp ser cys asn gln gly arg tyr pro leu ile gln thr leu arg gln glu asp thr phe cys gln gly lys ala asp gly leu tyr pro asn pro arg pro trp gly ser ala ala lys leu val cys tyr phe thr asn trp ala gln tyr arg gln gly glu ala arg phe leu pro lys asp leu asp pro ser leu cys thr his leu ile tyr ala phe ala gly met thr asn his gly gly trp asn phe gly thr gln lys phe thr asp met val ala thr gln gly ser pro ala val asp lys glu arg phe thr thr leu val gln asp leu ala asn ala phe gln gln glu ala gln thr ser gly lys glu arg leu leu leu ser ala ala val pro ala gly gln thr tyr val asp ala gly tyr glu val asp lys ile ala gln asn leu asp phe val asn leu met ala tyr asp phe his gly ser trp glu lys val thr gly his asn ser pro leu tyr lys arg gln glu glu ser gly ala ala ala ser leu asn val asp ala ala val gln gln trp leu gln lys gly thr pro ala ser lys leu ile leu gly met pro thr tyr gly arg ser phe thr glu val cys ser trp lys gly ala thr lys gln arg ile gln asp gln lys val pro tyr ile phe arg asp asn gln trp val gly phe asp asp ser cys asn gln gly arg tyr pro leu ile gln thr leu arg gln glu