# Patent

## Title
Enzymatic hydroxylation of aliphatic hydrocarbon

## Abstract

The invention relates to enzymatic methods for hydroxylation in position 2 or 3 of substituted or unsubstituted, linear or branched aliphatic hydrocarbons.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a 35 U.S.C. 371 national application of PCT/EP2011/054761 filed Mar. 28, 2011, which claims priority or the benefit under 35 U.S.C. 119 of European application nos. 10158092.6 and 10158093.4, both filed Mar. 28, 2010, and U.S. provisional application No. 61/318,582 filed on Mar. 29, 2010, the contents of which are fully incorporated herein by reference.


REFERENCE TO A SEQUENCE LISTING
This application contains a Sequence Listing in computer readable form. The computer readable form is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the use of polypeptides having peroxygenase activity for site specific hydroxylation of aliphatic hydrocarbons.
2. Background
A peroxygenase denoted AaP from the agaric basidiomycete strain Agrocybe aegerita (strain TM-A1) was found to oxidize aryl alcohols and aldehydes. The AaP peroxygenase was purified from A. aegerita TM A1 by several steps of ion chromatography and SDS-PAGE, the molecular weight was determined and the N-terminal 14 amino acid sequence was determined after 2-D electrophoresis but the encoding gene was not isolated (Ullrich et al., 2004, Appl. Env. Microbiol. 70 (8): 4575-4581).
WO 2006/034702 discloses methods for the enzymatic hydroxylation of non-activated hydrocarbons, such as, naphtalene, toluol and cyclohexane, using the AaP peroxygenase enzyme of Agrocybe aegerita TM A1. This is also described in Ullrich and Hofrichter, 2005, FEBS Letters 579: 6247-6250.
WO 2008/119780 discloses eight different peroxygenases from Agrocybe aegerita, Coprinopsis cinerea, Laccaria bicolor and Coprinus radians; also shown as SEQ ID NOs:1-8 in the present application.
DE 103 32 065 A1 discloses methods for the enzymatic preparation of acids from alcohols through the intermediary formation of aldehydes by using the AaP peroxygenase enzyme of Agrocybe aegerita TM A1.
A method was reported for the rapid and selective spectrophotometric direct detection of aromatic hydroxylation by the AaP peroxygenase (Kluge et al., 2007, Appl Microbiol Biotechnol 75: 1473-1478).
It is well-known that a direct regioselective introduction of oxygen functions (oxygenation) into organic molecules constitutes a problem in chemical synthesis. It is particularly difficult to catalyse the selective hydroxylation of aliphatic carbohydrates. The products may be used as important intermediates in a wide variety of different syntheses.
In particular the chemical hydroxylation of alkanes is relatively complex, requires aggressive/toxic chemicals/catalysts and leads to a series of undesired by-products.
It is known that an intracellular enzyme, methane monooxygenase (MMO, EC 14.13.25), oxygenates/hydroxylates the terminal carbon of some hydrocarbons. The MMO enzyme consists of several protein components and is formed by methylotrophic bacteria (e.g. Methylococcus capsulatus); it requires complex electron donors such as NADH or NADPH, auxiliary proteins (flavin reductases, regulator protein) and molecular oxygen (O2). The natural substrate of MMO is methane, which is oxidized to methanol. As a particularly unspecific biocatalyst, MMO oxygenates/hydroxylates, as well as methane, a series of further substrates such as n-alkanes and their derivatives, cycloalkanes, aromatics, carbon monoxide and heterocycles. Utilization of the enzyme in biotechnology is currently not possible, since it is difficult to isolate, like most intracellular enzymes, it is of low stability, and the cosubstrates required are relatively expensive.
SUMMARY OF THE INVENTION
In a first aspect, the inventors of the present invention have provided a method for hydroxylation in position 2 or 3 of either end of a substituted or unsubstituted, linear or branched, aliphatic hydrocarbon having at least 3 carbons and having a hydrogen attached to the carbon in position 2 or 3, comprising contacting the aliphatic hydrocarbon with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide comprises:
a) an amino acid sequence which has at least 50% identity to SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8; and
b) an amino acid sequence represented by one or more of the following motifs:









Motif I:



(SEQ ID NO: 9)



[FL]XX[YF]S[AN]X[FHY]G[GN]GX[YF]N;



 



Motif II:



(SEQ ID NO: 10)



G[GN]GX[YF]NXX[VA]AX[EH][LF]R;



 



Motif III:



(SEQ ID NO: 11)



RXXRI[QE][DEQ]S[IM]ATN;



 



Motif IV:



(SEQ ID NO: 12)



S[IM]ATN[PG][EQN][FM][SDN][FL];



 



Motif V:



(SEQ ID NO: 13)



P[PDK][DG]F[HFW]R[AP];



 



Motif VI:



(SEQ ID NO: 14)



[TI]XXXLYPNP[TK][GV].






In an embodiment, the aliphatic hydrocarbon is a fatty acid.
In another aspect is provided a method for hydroxylation in position 2 or 3 of the terminal end of an acyl group of a lipid, comprising contacting the lipid with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide comprises:
a) an amino acid sequence which has at least 50% identity to SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8; and
b) an amino acid sequence represented by one or more of the following motifs:









Motif I:



(SEQ ID NO: 9)



[FL]XX[YF]S[AN]X[FHY]G[GN]GX[YF]N



 



Motif II:



(SEQ ID NO: 10)



G[GN]GX[YF]NXX[VA]AX[EH][LF]R



 



Motif III:



(SEQ ID NO: 11)



RXXRI[QE][DEQ]S[IM]ATN



 



Motif IV:



(SEQ ID NO: 12)



S[IM]ATN[PG][EQN][FM][SDN][FL]



 



Motif V:



(SEQ ID NO: 13)



P[PDK][DG]F[HFW]R[AP]



 



Motif VI:



(SEQ ID NO: 14)



[TI]XXXLYPNP[TK][GV].






In further aspects, the invention provides uses of polypeptides having peroxygenase activity for removal of lipid containing stains from laundry; and for reducing unpleasant odor from laundry.
DEFINITIONS
Peroxygenase activity: The term “peroxygenase activity” is defined herein as the capability to hydroxylate naphtalene using hydrogen peroxide, also referred to as “unspecific peroxygenase”, EC 1.11.2.1. This is a heme-thiolate protein. Enzymes of this type include glycoproteins secreted by agaric basidiomycetes. They catalyse the insertion of an oxygen atom from H2O2 into a wide variety of substrates, including aromatic rings such as naphthalene, toluene, phenanthrene, pyrene and p-nitrophenol, recalcitrant heterocycles such as pyridine, dibenzofuran, various ethers (resulting in O-dealkylation) and alkanes such as propane, hexane and cyclohexane. Additional reactions which may be catalysed by peroxygenases include hydroxylation, epoxidation, N-oxidation, sulfooxidation, O- and N-dealkylation, bromination and one-electron oxidations. They have little or no activity toward chloride.
For purposes of the present invention, peroxygenase activity is determined according to the spectrophotometric procedure described by Kluge et al. (2007, Appl Microbiol Biotechnol 75: 1473-1478).
The polypeptides of the present invention have at least 20%, preferably at least 40%, more preferably at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, even more preferably at least 90%, most preferably at least 95%, and even most preferably at least 100% of the peroxygenase activity of the mature polypeptide of SEQ ID NO: 1, 2, 3, 4, 5, 6, 7 or 8.
Isolated polypeptide: The term “isolated polypeptide” as used herein refers to a polypeptide that is isolated from a source. In a preferred aspect, the polypeptide is at least 1% pure, preferably at least 5% pure, more preferably at least 10% pure, more preferably at least 20% pure, more preferably at least 40% pure, more preferably at least 60% pure, even more preferably at least 80% pure, and most preferably at least 90% pure, as determined by SDS-PAGE.
Substantially pure polypeptide: The term “substantially pure polypeptide” denotes herein a polypeptide preparation that contains at most 10%, preferably at most 8%, more preferably at most 6%, more preferably at most 5%, more preferably at most 4%, more preferably at most 3%, even more preferably at most 2%, most preferably at most 1%, and even most preferably at most 0.5% by weight of other polypeptide material with which it is natively or recombinantly associated. It is, therefore, preferred that the substantially pure polypeptide is at least 92% pure, preferably at least 94% pure, more preferably at least 95% pure, more preferably at least 96% pure, more preferably at least 96% pure, more preferably at least 97% pure, more preferably at least 98% pure, even more preferably at least 99%, most preferably at least 99.5% pure, and even most preferably 100% pure by weight of the total polypeptide material present in the preparation. The polypeptides of the present invention are preferably in a substantially pure form, i.e., that the polypeptide preparation is essentially free of other polypeptide material with which it is natively or recombinantly associated. This can be accomplished, for example, by preparing the polypeptide by well-known recombinant methods or by classical purification methods.
Mature polypeptide: The term “mature polypeptide” is defined herein as a polypeptide having peroxygenase activity that is in its final form following translation and any post-translational modifications, such as N-terminal processing, C-terminal truncation, glycosylation, phosphorylation, etc. In a preferred aspect, the mature polypeptide has the amino acid sequence shown in positions 1 to 330 of SEQ ID NO:1 based on the N-terminal peptide sequencing data (Ullrich et al., 2004, Appl. Env. Microbiol. 70 (8): 4575-4581), elucidating the start of the mature protein of AaP peroxygenase enzyme. In another preferred aspect, the mature polypeptide has the amino acid sequence shown in positions 1 to 328 of SEQ ID NO:2.
Identity: The relatedness between two amino acid sequences or between two nucleotide sequences is described by the parameter “identity”.
For purposes of the present invention, the degree of identity between two amino acid sequences is determined using the Needleman-Wunsch algorithm (Needleman and Wunsch, 1970, J. Mol. Biol. 48: 443-453) as implemented in the Needle program of the EMBOSS package (EMBOSS: The European Molecular Biology Open Software Suite, Rice et al., 2000, Trends in Genetics 16: 276-277; http://emboss.org), preferably version 3.0.0 or later. The optional parameters used are gap open penalty of 10, gap extension penalty of 0.5, and the EBLOSUM62 (EMBOSS version of BLOSUM62) substitution matrix. The output of Needle labeled “longest identity” (obtained using the -nobrief option) is used as the percent identity and is calculated as follows:

(Identical Residues×100)/(Length of Alignment−Total Number of Gaps in Alignment)

For purposes of the present invention, the degree of identity between two deoxyribonucleotide sequences is determined using the Needleman-Wunsch algorithm (Needleman and Wunsch, 1970, supra) as implemented in the Needle program of the EMBOSS package (EMBOSS: The European Molecular Biology Open Software Suite, Rice et al., 2000, supra; http://emboss.org), preferably version 3.0.0 or later. The optional parameters used are gap open penalty of 10, gap extension penalty of 0.5, and the EDNAFULL (EMBOSS version of NCBI NUC4.4) substitution matrix. The output of Needle labeled “longest identity” (obtained using the -nobrief option) is used as the percent identity and is calculated as follows:

(Identical Deoxyribonucleotides×100)/(Length of Alignment−Total Number of Gaps in Alignment).

Modification: The term “modification” means herein any chemical modification of the polypeptide consisting of the mature polypeptide of SEQ ID NO: 1, 2, 3, 4, 5, 6, 7 or 8; or a homologous sequence thereof; as well as genetic manipulation of the DNA encoding such a polypeptide. The modification can be a substitution, a deletion and/or an insertion of one or more (several) amino acids as well as replacements of one or more (several) amino acid side chains.


DETAILED DESCRIPTION OF THE INVENTION
Polypeptides Having Peroxygenase Activity (Peroxygenases)
The present invention relates to uses of an isolated polypeptide, which is preferably recombinantly produced, having peroxygenase activity, which comprises an amino acid sequence having at least 50% identity, preferably at least 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, or 98% identity to the polypeptide of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8.
In a preferred embodiment, the polypeptide comprises an amino acid sequence represented by one or more of the following motifs, preferably comprising two or more, three or more, four or more, five or six of the following motifs:









Motif I:



(SEQ ID NO: 9)



[FL]XX[YF]S[AN]X[FHY]G[GN]GX[YF]N;



 



Motif II:



(SEQ ID NO: 10)



G[GN]GX[YF]NXX[VA]AX[EH][LF]R;



 



Motif III:



(SEQ ID NO: 11)



RXXRI[QE][DEQ]S[IM]ATN;



 



Motif IV:



(SEQ ID NO: 12)



S[IM]ATN[PG][EQN][FM][SDN][FL];



 



Motif V:



(SEQ ID NO: 13)



P[PDK][DG]F[HFW]R[AP];



 



Motif VI:



(SEQ ID NO: 14)



[TI]XXXLYPNP[TK][GV].






In another embodiment, the polypeptide comprises an amino acid sequence having a substitution, deletion, and/or insertion of one or several amino acids of the mature polypeptide of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8.
In yet another embodiment, the polypeptide of the first aspect comprises or consists of the amino acid sequence of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8; or a fragment thereof having peroxygenase activity; preferably the polypeptide comprises or consists of the mature polypeptide of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8.
Preferably, amino acid changes are of a minor nature, that is conservative amino acid substitutions or insertions that do not significantly affect the folding and/or activity of the protein; small deletions, typically of one to about 30 amino acids; small amino- or carboxyl-terminal extensions, such as an amino-terminal methionine residue; a small linker peptide of up to about 20-25 residues; or a small extension that facilitates purification by changing net charge or another function, such as a poly-histidine tract, an antigenic epitope or a binding domain.
Examples of conservative substitutions are within the group of basic amino acids (arginine, lysine and histidine), acidic amino acids (glutamic acid and aspartic acid), polar amino acids (glutamine and asparagine), hydrophobic amino acids (leucine, isoleucine and valine), aromatic amino acids (phenylalanine, tryptophan and tyrosine), and small amino acids (glycine, alanine, serine, threonine and methionine). Amino acid substitutions that do not generally alter specific activity are known in the art and are described, for example, by H. Neurath and R. L. Hill, 1979, In, The Proteins, Academic Press, New York. The most commonly occurring exchanges are Ala/Ser, Val/Ile, Asp/Glu, Thr/Ser, Ala/Gly, Ala/Thr, Ser/Asn, Ala/Val, Ser/Gly, Tyr/Phe, Ala/Pro, Lys/Arg, Asp/Asn, Leu/Ile, Leu/Val, Ala/Glu, and Asp/Gly.
In addition to the 20 standard amino acids, non-standard amino acids (such as 4-hydroxyproline, 6-N-methyl lysine, 2-aminoisobutyric acid, isovaline, and alpha-methyl serine) may be substituted for amino acid residues of a wild-type polypeptide. A limited number of non-conservative amino acids, amino acids that are not encoded by the genetic code, and unnatural amino acids may be substituted for amino acid residues. “Unnatural amino acids” have been modified after protein synthesis, and/or have a chemical structure in their side chain(s) different from that of the standard amino acids. Unnatural amino acids can be chemically synthesized, and preferably, are commercially available, and include pipecolic acid, thiazolidine carboxylic acid, dehydroproline, 3- and 4-methylproline, and 3,3-dimethylproline.
Alternatively, the amino acid changes are of such a nature that the physico-chemical properties of the polypeptides are altered. For example, amino acid changes may improve the thermal stability of the polypeptide, alter the substrate specificity, change the pH optimum, and the like.
Essential amino acids in the parent polypeptide can be identified according to procedures known in the art, such as site-directed mutagenesis or alanine-scanning mutagenesis (Cunningham and Wells, 1989, Science 244: 1081-1085). In the latter technique, single alanine mutations are introduced at every residue in the molecule, and the resultant mutant molecules are tested for biological activity (i.e., peroxygenase activity) to identify amino acid residues that are critical to the activity of the molecule. See also, Hilton et al., 1996, J. Biol. Chem. 271: 4699-4708. The active site of the enzyme or other biological interaction can also be determined by physical analysis of structure, as determined by such techniques as nuclear magnetic resonance, crystallography, electron diffraction, or photoaffinity labeling, in conjunction with mutation of putative contact site amino acids. See, for example, de Vos et al., 1992, Science 255: 306-312; Smith et al., 1992, J. Mol. Biol. 224: 899-904; Wlodaver et al., 1992, FEBS Lett. 309: 59-64. The identities of essential amino acids can also be inferred from analysis of identities with polypeptides that are related to a polypeptide according to the invention.
Single or multiple amino acid substitutions, deletions, and/or insertions can be made and tested using known methods of mutagenesis, recombination, and/or shuffling, followed by a relevant screening procedure, such as those disclosed by Reidhaar-Olson and Sauer, 1988, Science 241: 53-57; Bowie and Sauer, 1989, Proc. Natl. Acad. Sci. USA 86: 2152-2156; WO 95/17413; or WO 95/22625. Other methods that can be used include error-prone PCR, phage display (e.g., Lowman et al., 1991, Biochem. 30: 10832-10837; U.S. Pat. No. 5,223,409; WO 92/06204), and region-directed mutagenesis (Derbyshire et al., 1986, Gene 46: 145; Ner et al., 1988, DNA 7: 127).
Mutagenesis/shuffling methods can be combined with high-throughput, automated screening methods to detect activity of cloned, mutagenized polypeptides expressed by host cells (Ness et al., 1999, Nature Biotechnology 17: 893-896). Mutagenized DNA molecules that encode active polypeptides can be recovered from the host cells and rapidly sequenced using standard methods in the art. These methods allow the rapid determination of the importance of individual amino acid residues in a polypeptide of interest, and can be applied to polypeptides of unknown structure.
The total number of amino acid substitutions, deletions and/or insertions of the mature polypeptide of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7 or SEQ ID NO:8 is 10, preferably 9, more preferably 8, more preferably 7, more preferably at most 6, more preferably 5, more preferably 4, even more preferably 3, most preferably 2, and even most preferably 1.
It is preferable that the polypeptide of the first aspect is encoded by the polynucleotide contained in the plasmid which is contained in E. coli NN049991 deposited 14 Mar. 2008 under the terms of the Budapest Treaty with the DSMZ under accession number DSM 21289; or which is encoded by the polynucleotide contained in the plasmid which is contained in E. coli NN049992 deposited 14 Mar. 2008 under the terms of the Budapest Treaty with the DSMZ under accession number DSM 21290.
Another preferred embodiment relates to the polypeptide of the first aspect of the invention, wherein the mature polypeptide is amino acids 1 to 330 of SEQ ID NO:1.
Yet another preferred embodiment relates to the polypeptide of the first aspect of the invention, wherein the mature polypeptide is amino acids 1 to 328 of SEQ ID NO:2.
Yet another preferred embodiment relates to the polypeptide of the first aspect of the invention, wherein the mature polypeptide is amino acids 1 to 344 of SEQ ID NO:4.
Hydrogen Peroxide
The hydrogen peroxide required by the peroxygenase may be provided as an aqueous solution of hydrogen peroxide or a hydrogen peroxide precursor for in situ production of hydrogen peroxide. Any solid entity which liberates upon dissolution a peroxide which is useable by peroxygenase can serve as a source of hydrogen peroxide. Compounds which yield hydrogen peroxide upon dissolution in water or an appropriate aqueous based medium include but are not limited to metal peroxides, percarbonates, persulphates, perphosphates, peroxyacids, alkylperoxides, acylperoxides, peroxyesters, urea peroxide, perborates and peroxycarboxylic acids or salts thereof.
Another source of hydrogen peroxide is a hydrogen peroxide generating enzyme system, such as an oxidase together with a substrate for the oxidase. Examples of combinations of oxidase and substrate comprise, but are not limited to, amino acid oxidase (see e.g. U.S. Pat. No. 6,248,575) and a suitable amino acid, glucose oxidase (see e.g. WO 95/29996) and glucose, lactate oxidase and lactate, galactose oxidase (see e.g. WO 00/50606) and galactose, and aldose oxidase (see e.g. WO 99/31990) and a suitable aldose.
By studying EC 1.1.3._, EC 1.2.3._, EC 1.4.3._, and EC 1.5.3.— or similar classes (under the International Union of Biochemistry), other examples of such combinations of oxidases and substrates are easily recognized by one skilled in the art.
Hydrogen peroxide or a source of hydrogen peroxide may be added at the beginning of or during the method of the invention, e.g. as one or more separate additions of hydrogen peroxide; or continuously as fed-batch addition. Typical amounts of hydrogen peroxide correspond to levels of from 0.001 mM to 25 mM, preferably to levels of from 0.005 mM to 5 mM, and particularly to levels of from 0.01 to 1 mM hydrogen peroxide. Hydrogen peroxide may also be used in an amount corresponding to levels of from 0.1 mM to 25 mM, preferably to levels of from 0.5 mM to 15 mM, more preferably to levels of from 1 mM to 10 mM, and most preferably to levels of from 2 mM to 8 mM hydrogen peroxide.
Surfactants
The method of the invention may include application of a surfactant (for example, as part of a detergent formulation or as a wetting agent). Surfactants suitable for being applied may be non-ionic (including semi-polar), anionic, cationic and/or zwitterionic; preferably the surfactant is anionic (such as linear alkylbenzenesulfonate, alpha-olefinsulfonate, alkyl sulfate (fatty alcohol sulfate), alcohol ethoxysulfate, secondary alkanesulfonate, alpha-sulfo fatty acid methyl ester, alkyl- or alkenylsuccinic acid or soap) or non-ionic (such as alcohol ethoxylate, nonylphenol ethoxylate, alkylpolyglycoside, alkyldimethylamineoxide, ethoxylated fatty acid monoethanolamide, fatty acid monoethanolamide, polyhydroxy alkyl fatty acid amide, or N-acyl N-alkyl derivatives of glucosamine (“glucamides”)), or a mixture thereof.
When included in the method of the invention, the concentration of the surfactant will usually be from about 0.01% to about 10%, preferably about 0.05% to about 5%, and more preferably about 0.1% to about 1% by weight.
Aliphatic Hydrocarbons
The hydrocarbons, which are hydroxylated in the method of the invention, are aliphatic hydrocarbons having a chain of at least 3 carbons, and having a hydrogen attached to the carbon in position 2 or 3. Preferably, the aliphatic hydrocarbon is an alkane or an alkene; more preferably, the aliphatic hydrocarbon is an alkane, such as propane, butane, pentane, hexane, heptane, octane, nonane or decane, or isomers thereof.
The aliphatic hydrocarbons are linear or branched, but not cyclic, as site specific hydroxylation is not possible with cyclic hydrocarbons. Branched hydrocarbons correspond to isomers of linear hydrocarbons.
The aliphatic hydrocarbons are substituted or unsubstituted. Preferably, the aliphatic hydrocarbons are unsubstituted, such as non-activated hydrocarbons.
When the aliphatic hydrocarbons are substituted (functional groups attached), the preferred substituents are halogen, hydroxyl, carboxyl, amino, nitro, cyano, thiol, sulphonyl, formyl, acetyl, methoxy, ethoxy, phenyl, benzyl, xylyl, carbamoyl and sulfamoyl; more preferred substituents are chloro, hydroxyl, carboxyl and sulphonyl; and most preferred substituents are chloro and carboxyl.
The aliphatic hydrocarbons may be substituted by up to 10 substituents, up to 8 substituents, up to 6 substituents, up to 4 substituents, up to 2 substituents, or by up to one substituent.
In a preferred embodiment, the aliphatic hydrocarbon is a fatty acid (the substituent is a carboxyl group). Examples of fatty acids include, but are not limited to, butanoic acid (butyric acid), pentanoic acid (valeric acid), hexanoic acid (caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), eicosanoic acid (arachidic acid), linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid.
In a second aspect, the aliphatic hydrocarbon is an acyl group of a lipid, such as a monoglyceride, diglyceride, triglyceride, phospholipid or sphingolipid; and the hydroxylation takes place in position 2 or position 3 of the terminal end of the acyl group. The acyl group must have at least one hydrogen attached to the carbon in position 2 or 3 of the terminal end. The acyl group may be saturated or unsaturated, and optionally functional groups (substituents) may be attached. Examples of acyl groups include, but are not limited to, the acyl forms of butanoic acid (butyric acid), pentanoic acid (valeric acid), hexanoic acid (caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), eicosanoic acid (arachidic acid), linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid.
Methods and Uses
The present invention provides a method for site specific hydroxylation in position 2 or position 3 of an aliphatic hydrocarbon using a peroxygenase and hydrogen peroxide. The aliphatic hydrocarbon must include a chain of at least 3 carbons, and either (one or more) end of the aliphatic hydrocarbon may be used as the starting point to determine which carbon is in position 2 or 3. The aliphatic hydrocarbon must have at least one hydrogen attached to the carbon (which is hydroxylated) in position 2 or 3. In a preferred embodiment, the carbon in position 2 or 3, which is hydroxylated with the peroxygenase, is unsubstituted (before the hydroxylation is carried out).
Accordingly, in a first aspect, the present invention provides a method for hydroxylation in position 2 or 3 of either end (one or more ends) of a substituted or unsubstituted, linear or branched, aliphatic hydrocarbon having at least 3 carbons and having a hydrogen attached to the carbon in position 2 or 3, comprising contacting the aliphatic hydrocarbon with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide comprises:
a) an amino acid sequence which has at least 50% identity to SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8; and
b) an amino acid sequence represented by one or more of the following motifs:









Motif I:



(SEQ ID NO: 9)



[FL]XX[YF]S[AN]X[FHY]G[GN]GX[YF]N;



 



Motif II:



(SEQ ID NO: 10)



G[GN]GX[YF]NXX[VA]AX[EH][LF]R;



 



Motif III:



(SEQ ID NO: 11)



RXXRI[QE][DEQ]S[IM]ATN;



 



Motif IV:



(SEQ ID NO: 12)



S[IM]ATN[PG][EQN][FM][SDN][FL];



 



Motif V:



(SEQ ID NO: 13)



P[PDK][DG]F[HFW]R[AP];



 



Motif VI:



(SEQ ID NO: 14)



[TI]XXXLYPNP[TK][GV].






The method of the invention may be used for a variety of purposes, like bulk chemical synthesis (biocatalysis), increasing aqueous solubility of aliphatic hydrocarbons, bioremediation, and modification of the characteristics of food products.
The method of the invention may also be used for a number of industrial processes in which said hydroxylation reactions are beneficial. An example of such use is in the manufacture of pulp and paper products where alkanes and other relevant aliphatic hydrocarbons that are present in the wood (resin) can result in depositioning problems in the pulp and paper manufacturing process. These hydrophobic compounds are the precursors of the so-called pitch deposits within the pulp and paper manufacturing processes. Pitch deposition results in low quality pulp, and can cause the shutdown of pulp mill operations. Specific issues related to pulps with high extractives content include runnability problems, spots and holes in the paper, and sheet breaks. Treatment with peroxygenase can increase the solubility of said compounds and thereby mitigate problems.
Yet another use of the method of the invention is in i.e. oil or coal refineries where the peroxygenase catalyzed hydroxylation can be used to modify the solubility, viscosity and/or combustion characteristics of hydrocarbons. Specifically the treatment can lead to changes in the smoke point, the kindling point, the fire point and the boiling point of the hydrocarbons subjected to the treatment.
In the synthesis of bulk chemicals, agro chemicals (incl. pesticides), specialty chemicals and pharmaceuticals the method of the invention may obviously be relevant in terms of selectively introducing hydroxy groups in the substrates thereby affecting the solubility of the modified compound. Furthermore, the selective hydroxylation provides a site for further modification by methods known in the art of organic chemical synthesis and chemo-enzymatic synthesis.
Natural gas is extensively processed to remove higher alkanes. Hydroxylation of such higher alkanes may be used to improve water solubility, and thus facilitate removal of the higher alkanes by washing the natural gas stream. Removal may be performed at the well or during refining.
Hydroxylation of oil waste will significantly improve biodegradability and will be applicable both in connection with waste water treatment from refineries and bioremediation of contaminated ground or water
In a second aspect, the present invention provides a method for hydroxylation in position 2 or 3 of the terminal end of an acyl group of a lipid, comprising contacting the lipid with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide comprises:
a) an amino acid sequence which has at least 50% identity to SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, or SEQ ID NO:8; and
b) an amino acid sequence represented by one or more of the following motifs:









Motif I:



(SEQ ID NO: 9)



[FL]XX[YF]S[AN]X[FHY]G[GN]GX[YF]N



 



Motif II:



(SEQ ID NO: 10)



G[GN]GX[YF]NXX[VA]AX[EH][LF]R



 



Motif III:



(SEQ ID NO: 11)



RXXRI[QE][DEQ]S[IM]ATN



 



Motif IV:



(SEQ ID NO: 12)



S[IM]ATN[PG][EQN][FM][SDN][FL]



 



Motif V:



(SEQ ID NO: 13)



P[PDK][DG]F[HFW]R[AP]



 



Motif VI:



(SEQ ID NO: 14)



[TI]XXXLYPNP[TK][GV].






Hydroxylation of the acyl group of a lipid generally improves the aqueous solubility of the lipid. Accordingly, the method of the invention may be used to remove or reduce oil or lipid containing stains, like chocolate, from laundry, by contacting the laundry with a peroxygenase and a source of hydrogen peroxide, and optionally a surfactant.
The methods of the invention may be carried out with an immobilized polypeptide having peroxygenase activity (peroxygenase).
The methods of the invention may be carried out in an aqueous solvent (reaction medium), various alcohols, ethers, other polar or non-polar solvents, or mixtures thereof. By studying the characteristics of the aliphatic hydrocarbon used in the methods of the invention, suitable examples of solvents are easily recognized by one skilled in the art. By raising or lowering the pressure at which the hydroxylation is carried out, the solvent (reaction medium) and the aliphatic hydrocarbon can be maintained in a liquid phase at the reaction temperature.
The methods according to the invention may be carried out at a temperature between 0 and 90 degrees Celsius, preferably between 5 and 80 degrees Celsius, more preferably between 10 and 70 degrees Celsius, even more preferably between 15 and 60 degrees Celsius, most preferably between 20 and 50 degrees Celsius, and in particular between 20 and 40 degrees Celsius.
The methods of the invention may employ a treatment time of from 10 seconds to (at least) 24 hours, preferably from 1 minute to (at least) 12 hours, more preferably from 5 minutes to (at least) 6 hours, most preferably from 5 minutes to (at least) 3 hours, and in particular from 5 minutes to (at least) 1 hour.
In another aspect, the methods of the invention may be used to reduce unpleasant odors from laundry by contacting the laundry with a peroxygenase and a source of hydrogen peroxide, and optionally a surfactant. The method of the invention results in reduction of the amount of butanoic acid (butyric acid) in the laundry. Butanoic acid is formed during washing of laundry when certain animal fats and plant oils are hydrolyzed, e.g. by detergent lipase, to yield free fatty acids, including butanoic acid. Butanoic acid has an extremely unpleasant odor. The peroxygenase hydroxylates the butanoic acid to 2-hydroxybutyric acid (alpha-hydroxybutyric acid) or 3-hydroxybutyric acid (beta-hydroxybutyric acid).
Unless otherwise specified, the nomenclature used is standard IUPAC nomenclature.
The present invention is further described by the following examples that should not be construed as limiting the scope of the invention.
EXAMPLES
The polypeptide having peroxygenase activity from Agrocybe aegerita, which is shown as SEQ ID NO:2, is referred to as AaeAPO in the following examples.
Example 1
Hydroxylation of N-Hexane
Enzymatic hydroxylation of hexane was performed in the pure substrate (n-hexane, >97%, Sigma Aldrich) containing 2 U ml−1 (0.31 nmol) AaeAPO added as aqueous enzyme solution (10 μl). H2O2 (4 mM) was added by syringe pumps over 1 hour. The experiment was done in 200 μl scale (total volume) in 1 ml glass vials stirred with a magnetic stirrer. Products were analyzed by GC-MS (Varian) by direct injection of the reaction mixture. Controls were processed identically except that water (10 μl) was added instead of enzyme solution.
The gas chromatogram and mass spectra of the sample with active enzyme (AaeAPO) and n-hexane showed formation of high amounts of 2-hexanol, and 3-hexanol; the control without enzyme did not contain any of these peaks.
Example 2
Hydroxylation of N-Decane
Enzymatic conversion (in 200 μl total volume) was done in pure n-decane (>97%, Sigma Aldrich) supplemented with 2 U ml−1 (0.31 nmol) AaeAPO. H2O2 (8 mM) was added by syringe pumps over 2 hours and the sample was stirred with a magnetic stirrer. Products were measured by GC-MS. Controls were processed identically except that water (10 μl) was added instead of enzyme.
The gas chromatogram and mass spectra of the sample with active enzyme (AaeAPO) and n-decane showed formation of high amounts of two n-alkanols, 3-decanol and 2-decanol; the control without enzyme did not contain these peaks.
Example 3
Enzymatic Hydroxylation of Lauric Acid
Enzymatic hydroxylation of lauric acid was performed using a total reaction mixture of 4 ml containing 50 mM potassium phosphate buffer, 40 v/v % acetronitrile, 1 mM lauric acid (>98% pure, Aldrich W261408 was dissolved in acetonitrile), 0.01 mg peroxygenase protein/ml (the peroxygenase shown as SEQ ID NO:4) and 2 mM ascorbic acid was added according to the table below.
The reaction was started by addition of hydrogen peroxide corresponding to a concentration of 0.5 mM in the reaction mixture. The reaction mixtures were incubated for 60 minutes at 35° C. using a heat block. A second addition of peroxide was added after 30 minutes incubation to a total concentration of 1 mM. The reactions were stopped by a heat treatment of 85° C. in a water bath for 5 minutes. Products were measured by GC-FID (Varian 3900) by injection at 100° C. in split mode with ratio of 10:1 (helium was used as carrier gas at a constant flow of 25 ml/min). A temperature gradient were applied heating to 200° C. at a rate of 10° C./min, then proceeding to 360° C. at a rate of 50° C./min. The results were recorded as peak area (see Table 1).









TABLE 1






Lauric acid
Product


Treatment
(Area @3.2 min)
(Area @4.3 min)







Peroxygenase + H2O2
No peak
No peak


Lauric acid + H2O2 + ascorbic acid
16011
91


Lauric acid + peroxygenase +
14406
395.5


H2O2 + ascorbic acid









A product peak appeared in the presence of the peroxygenase. The elution time of the product was slightly shifted compared to 12-Hydroxydodecanoic acid, which is an iso-form of 2-hydroxy lauric acid and 3-hydroxy lauric acid. Hence, the elution time was in accordance to the expected product hydroxylated in the 2 or 3 position.
Example 4
Enzymatic Hydroxylation of Palmitic Acid
Enzymatic hydroxylation of palmitic acid was performed using a total reaction mixture of 4 ml containing 50 mM potassium phosphate buffer, 40 v/v % acetronitrile, 1 mM palmitic acid (>99% pure, Sigma P0500) and 0.01 mg peroxygenase protein/ml (the peroxygenase shown as SEQ ID NO:4).
The reaction was started by addition of hydrogen peroxide corresponding to a concentration of 1 mM in the reaction mixture. The reaction mixtures were incubated for 1, 2, 3 and 10 minutes at 35° C. using a heat block. The reactions were stopped by a heat treatment of 85° C. in a water bath for 5 minutes. Products were measured by GC-FID (Varian 3900) by injection at 100° C. in split mode with ratio of 10:1 (helium was used as carrier gas at a constant flow of 25 ml/min). A temperature gradient were applied heating to 200° C. at a rate of 10° C./min, then proceeding to 360° C. at a rate of 50° C./min. The results were recorded as peak area (see Table 2).









TABLE 2





Incubation time
Palmitic acid
Product


(min)
(Area)
(Area)

















0
1799.5
No peak


1
1481.2
82.8


2
979.1
191.3









A product peak appeared already after 1 minutes of incubation, and increased after two minutes incubation. The elution profile was slightly shifted compared to 16-Hydroxyhexadecanoic acid, which is an iso-form of 2-hydroxy palmitic and 3-hydroxy palmitic. Hence, the elution time was in accordance to the expected product hydroxylated in the 2 or 3 position.

## Claims

1. A method for hydroxylation in position 2 or 3 of either end of a substituted or unsubstituted, linear or branched, aliphatic hydrocarbon having at least 3 carbons and having a hydrogen attached to the carbon in position 2 or 3, comprising contacting the aliphatic hydrocarbon with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide has at least 90% sequence identity to SEQ ID NO:4.

2. The method of claim 1, wherein the carbon in position 2 or 3, which is hydroxylated, is unsubstituted until it is contacted with the peroxygenase.

3. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:9.

4. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:10.

5. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:11.

6. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:12.

7. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:13.

8. The method of claim 1, wherein the amino acid sequence of the polypeptide comprises SEQ ID NO:14.

9. The method of claim 1, wherein the polypeptide has at least 95% sequence identity to SEQ ID NO:4.

10. The method of claim 1, wherein the polypeptide comprises or consists of the amino acid sequence of SEQ ID NO:4.

11. The method of claim 1, wherein the polypeptide is a fragment thereof having peroxygenase activity.

12. The method of claim 1, wherein the substituents of the aliphatic hydrocarbon are selected from the group consisting of halogen, hydroxyl, carboxyl, amino, nitro, cyano, thiol, sulphonyl, formyl, acetyl, methoxy, ethoxy, phenyl, benzyl, xylyl, carbamoyl and sulfamoyl.

13. The method of claim 1, wherein the substituents are selected from the group consisting of chloro, hydroxyl, carboxyl and sulphonyl; in particular chloro and carboxyl.

14. The method of claim 1, wherein the aliphatic hydrocarbon is unsubstituted.

15. The method of claim 1, wherein the aliphatic hydrocarbon is linear.

16. The method of claim 1, wherein the aliphatic hydrocarbon is an alkane.

17. The method of claim 16, wherein the alkane is propane, butane, pentane, hexane, heptane, octane, nonane or decane, or isomers thereof.

18. The method of claim 1, wherein the aliphatic hydrocarbon is part of a fatty acid.

19. A method for hydroxylation in position 2 or 3 of the terminal end of an acyl group of a lipid, comprising contacting the lipid with hydrogen peroxide and a polypeptide having peroxygenase activity; wherein the polypeptide has at least 90% sequence identity to SEQ ID NO:4.

20. The method of claim 19, wherein the polypeptide has at least 95% identity to the mature polypeptide of SEQ ID NO:4.