Abstract:
The invention pertains to the field of reaction systems generating malodour, particularly from constituents of human sweat. Specifically, the invention pertains to proteins for generating malodours, substrates for generating such malodour, inhibitors of such malodour generation and test and screening systems for measuring their malodour inhibition efficacy and finding substances previously not known to inhibit malodour generation. Thus, the invention also pertains to the field of deodorants.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Phase entry of PCT/EP2011/073275, filed Dec. 19, 2011, which claims priority to European patent application number EP10195789.2 filed Dec. 17, 2010; and U.S. patent application No. 61/424,114, filed Dec. 17, 2010, which are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention pertains to the field of reaction systems generating malodour, particularly from constituents of human sweat. Specifically, the invention pertains to proteins for generating malodours, substrates for generating such malodour, inhibitors of such malodor generation and test and screening systems for measuring their malodour inhibition efficacy and finding substances previously not known to inhibit malodour generation. Thus, the invention also pertains to the field of deodorants. 
       REFERENCE TO THE SEQUENCE LISTING 
       [0003]    The Sequence Listing file identified as PF70045 BSE0137-00US_ST25.txt, created on Jun. 4, 2013, 105 KB, is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0004]    It is generally accepted that fresh human sweat is odorless, and that the smell of sweat is generated by microorganism colonizing the human skin and particularly the axilla. The smell thus generated from human sweat is considered characteristic in the sense that upon smelling such scent it is immediately clear that the scent indicates human sweat. The smell is widely and according to the present invention considered to be a malodour and can be very pronounced. 
         [0005]    It has thus been tried for ages to inhibit the generation of sweat malodour to reduce the malodour or to mask it. In the context of the present invention, “inhibition” designates all means to prevent the formation of sweat malodour from human sweat, including means for slowing down such malodour generation. “Reduction” refers to means for treating the constituents of sweat malodour to render them less intense, e.g. by binding to and immobilizing on a matrix. “Masking” designates those means and efforts intended to affect the human perception of sweat malodour, e.g. by overwhelming a human nose with other, more intense and less malodorous scents, or otherwise reducing or impairing the ability of the human olfactory system to detect one or more malodorous compounds of sweat malodour. 
         [0006]    It is desirable to inhibit the formation of sweat malodour and not only to reduce or mask such malodour. One way frequently tried is the application of antiperspirants to human axilla to prevent the formation of sweat. The reasoning is that when no sweat is formed, no sweat malodour will be generated. However, there are concerns that such influencing of human physiological processes may not be sustainable or lead to undesired side effects. In the context of the present invention “inhibitors” therefore are only those substances which are effective to slow down or prevent the formation of one or more constituent of sweat malodour from human sweat other than any relying predominant by on the suppression of secret formation. 
         [0007]    There is thus a general need to find effective inhibitors of sweat malodour generation. The search for such inhibitors is hampered by the fact that little is known about the actual formation of sweat malodour, particularly the physiological processes of microorganisms responsible for malodour generation. Further, there is a lack of standardized procedures to compare efficacy of potential malodour generation inhibitors. 
         [0008]    Document EP 1 387 891 (also published as WO 02/092024 A2) discloses an isolated N-alpha-acyl-glutamine-aminoacylase reportedly involved in the transformation of odourless precursor compounds found in sweat into malodorous fatty acids. The document further describes the application of this enzyme in high throughput screening for inhibitors. 
         [0009]    A disadvantage of the enzyme disclosed in the aforementioned European patent document and correspondingly also of the test system described therein is that the enzyme requires as a cofactor a zinc ion and is thus easily affected by the presence of chelating agents. However, zinc chelating agents like EDTA are not efficient for inhibiting the generation of human sweat malodour when applied to human sweat in vivo. Thus, the test system requires great care when preparing the reagents used therein, and potential inhibitors identified by the test system have to be reanalysed to rule out that their malodour inhibitory effect as determined by the test system is not merely a result of their interference with zinc ions. 
         [0010]    It was therefore a problem of the present invention to provide a test system for reproducing a representative pathway of sweat malodour generation without being dependent upon the presence of zinc ions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    According to the invention, there is thus provided a protein comprising an amino acid sequence having 
         [0012]    a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98% and most preferably of 100%, and/or 
         [0013]    b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99% and most preferably of 100%, 
         [0014]    to an amino acid sequence according to any of SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35 wherein the sequence identity and sequence similarity are computed according to the EMBOSS needle algorithm having a Gap Open penalty of 10.0, a Gap Extend penalty of 0.5 and using the Blosum62 matrix. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  illustrates SEQ ID NO:1. 
           [0016]      FIG. 2  illustrates SEQ ID NO:2. 
           [0017]      FIG. 3  illustrates SEQ ID NO:34. 
           [0018]      FIG. 4  illustrates SEQ ID NO:35. 
           [0019]      FIG. 5  illustrates SEQ ID NO:5. 
           [0020]      FIG. 6  illustrates SEQ ID NO:6. 
           [0021]      FIG. 7  illustrates SEQ ID NO:7. 
           [0022]      FIG. 8  illustrates SEQ ID NO:8. 
           [0023]      FIG. 9  illustrates SEQ ID NO:9. 
           [0024]      FIG. 10  illustrates SEQ ID NO:10. 
           [0025]      FIG. 11  illustrates SEQ ID NO:11. 
           [0026]      FIG. 12  illustrates SEQ ID NO:12. 
           [0027]      FIG. 13  illustrates SEQ ID NO:13. 
           [0028]      FIG. 14  illustrates SEQ ID NO:14. 
           [0029]      FIG. 15  illustrates SEQ ID NO:15. 
           [0030]      FIG. 16  illustrates SEQ ID NO:16. 
           [0031]      FIG. 17  illustrates SEQ ID NO:17. 
           [0032]      FIG. 18  illustrates SEQ ID NO:18. 
           [0033]      FIG. 19  illustrates SEQ ID NO:19. 
           [0034]      FIG. 20  illustrates SEQ ID NO:20. 
           [0035]      FIG. 21  illustrates SEQ ID NO:21. 
           [0036]      FIG. 22  illustrates SEQ ID NO:22. 
           [0037]      FIG. 23  illustrates SEQ ID NO:23. 
           [0038]      FIG. 24  illustrates SEQ ID NO: 24. 
           [0039]      FIG. 25  illustrates SEQ ID NO:25. 
           [0040]      FIG. 26  illustrates SEQ ID NO:26. 
           [0041]      FIG. 27  illustrates SEQ ID NO:27. 
           [0042]      FIG. 28  illustrates SEQ ID NO:28. 
           [0043]      FIG. 29  illustrates SEQ ID NO:29. 
           [0044]      FIG. 30  illustrates SEQ ID NO:30. 
           [0045]      FIG. 31  illustrates SEQ ID NO:31. 
           [0046]      FIG. 32  illustrates SEQ ID NO:32. 
           [0047]      FIG. 33  illustrates SEQ ID NO:33. 
           [0048]      FIG. 34  is an SDS-PAGE analysis showing the results of Example 2. 
           [0049]      FIG. 35  is a bar graph showing the enzyme activity results obtained in Example 3. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    It has been found that such protein is capable of quickly producing the characteristic malodour of human sweat when brought into contact with fresh, non-malodorous or weakly malodorous human sweat. Significantly, the ability to generate sweat malodour was also found upon contacting of the protein with sterilised human sweat. 
         [0051]    Even more important, it has been found that malodour generation from human sweat by this protein does not depend on the presence of zinc ions. The protein also retains its ability to cleave N-alpha-lauroyl-L-glutamine to release a biochemically easy to detect and quantify lauroyl fatty acid even in the presence of concentrations of EDTA sufficient for complexing zinc ions. The protein which is believed to be an enzyme is therefore useful in a malodour standard system and for screening of sweat malodour inhibitors. Even more beneficial, the protein has been found to have a high sequence similarity to proteins found in a huge variety of organisms of different genus, family, order, class and even phylum. The protein of the present invention is thus a representative of a ubiquitous set of proteins of hitherto unknown function occurring in a significant fraction of all microorganisms colonizing the human skin and particularly the axilla. Thus, it is to be expected that inhibitors effective for inhibition of malodour formation by a protein of the present invention will generally be effective to inhibit sweat malodour formation also when applied to human sweat in vivo and to the human skin. 
         [0052]    The protein of the present invention preferably is available in isolated form. “Isolated” in the context of the present invention designates that the protein is removed from its original environment and particularly is not contaminated with other microorganism material useful in producing the protein. Even more preferably, the protein is in purified form, which means that the content of the protein in a composition relative to other proteins or peptides having a length of at least 10 amino acids and relative to nucleic acids is at least 80 wt.-%, more particularly at least 90 wt.-%, still more particularly 95 wt.-% and most particularly 99 wt,-% or greater. 
         [0053]    The protein, preferably in isolated and even more preferably in purified form, comprises an amino acid sequence having the above sequence identity and/or sequence similarity to an amino acid sequence according to any of SEQ ID NO:2 to 31 ( FIG. 2  and  FIGS. 5-31 ), SEQ ID NO:34 ( FIG. 3 ), or SEQ ID NO:35 ( FIG. 4 ). Sequence identity and sequence similarity in the context of the present invention are determined according to the EMBOSS “needle” algorithm. This algorithm is the standard algorithm for pairwise amino acid sequence alignments covering the whole length of both sequences. The algorithm implements the Needleman-Wunsch algorithm (Needleman S. B. and Wunsch C. D., 1970 J. Mol. Biol. 48, 443-453), wherein a penalty for a gap of n positions is computed according to the formula 
         [0000]      gap opening penalty+(n−1)×gap extension penalty.
 
         [0054]    The entire length of each amino acid sequence is aligned, and there is no penalty for hanging ends of the overlap. 
         [0055]    Gap Open penalty in the context of the present invention is 10.0. The gap extension penalty in the context of the present invention is 0.5. The scoring matrix for comparing amino acid similarities in the context of the present invention is the “Blosum62” matrix. The Gap Open penalty, gap extend penalty and Blosum62 matrix are standard parameters used in the art. Sequence alignments can be performed with these parameters, e.g. via publicly available free tools. For example, the EBI offers a free pairwise sequence alignment service with the parameters of the present invention via its assortment of internet tools. 
         [0056]    The protein of the present invention, particularly in an isolated or purified form, may consist of any of the amino acid sequences SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35, wherein optionally the N-terminal methionine is missing. Proteins having these amino acid sequences without any further added amino acids or modifications are particularly capable of generating the intense and typical malodour when brought into contact with odourless sterilised human sweat. In the context of the present invention, sterilised means that the sweat is filtered by sterile filtration, as known to persons skilled in the art, in particular having a filtration cutoff of 0.4 μm. 
         [0057]    The protein of the present invention, preferably in isolated or purified form, preferably comprises or consists of an amino acid sequence according to SEQ ID NO:3, even more preferably according to SEQ ID NO:4. These proteins have been found to be particularly useful for generating a strong and typical malodour of human sweat when brought into contact with sterilised, odourless fresh human sweat. According to the present invention the intensity and flavour of generated sweat malodour is classified by an expert panel of 10 trained odour experts, intensity and flavour being ranked on a scale of 0 (not detectable) to 9 (very intense/very typical). Such assessment is common in the art of odour analysis. 
         [0058]    It has particularly been found that proteins comprising isoleucine at position 216 and proline at position 219 of SEQ ID NO:3, e.g. proteins of SEQ ID NO:4, can be easily produced biotechnologically and are capable of producing strong and typical sweat malodour when brought into contact with sterilised fresh human sweat. It is thus preferred that the protein of the present invention comprises or consists of an amino acid sequence according to SEQ ID NO:2 or of a sequence according to any of SEQ ID NO:5 to 31. 
         [0059]    Among these, a protein of the present invention is particularly preferred comprising or consisting of the amino acid sequence SEQ ID NO:2. This protein has been isolated from a strain of Bacillus subtilis and was particularly found to quickly produce a strong and typical malodour when brought into contact fresh sterilised human sweat, such sweat, as indicated previously, being essentially odourless in its fresh and sterilised state. 
         [0060]    The protein of the present invention, particularly the isolated or purified protein comprising or consisting of an amino acid sequence according to any of SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35, preferably does not cleave 3-methyl-2-hexenic acid-amide and 3-methyl-2-hydroxy-hexanoic acid-amide but does cleave N-alpha-lauroyl-L-glutamine. As said before, the cleavage of N-alpha-lauroyl-L-glutamine by the protein is independent of the presence of zinc ions. 
         [0061]    According to the invention, there is further provided an isolated nucleic acid coding for a protein of the present invention i.e. a protein having a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98%, and/or b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99%, to an amino acid sequence according to any of SEQ ID NO:231, SEQ ID NO:34, or SEQ ID NO:35 as defined above. The nucleic acid preferably comprises or consists of a base sequence according to SEQ ID NO:32 ( FIG. 32 ) or SEQ ID:NO 33 ( FIG. 33 ). The nucleotide sequence according to SEQ ID NO:32 is particularly adapted to produce the protein of SEQ ID NO:2 in  Bacillus subtilis;  the nucleic acid comprising the base sequence according to SEQ ID NO:33 is particularly adapted to produce the protein of SEQ ID NO:2 in  E. coli  K12. The skilled person understands that the invention also comprises nucleic acids coding for the protein consisting of SEQ ID NO:2 optimised for expression by other microorganisms than  Bacillus subtilis  and  E. coli  K12, wherein such optimisation is according to the respective codon preference of the microorganism for each respective amino acid. 
         [0062]    The nucleic acid of the present invention therefore allows to produce a protein of the present invention biotechnologically, to facilitate the providing of such protein reproducibly and in sufficient quantities. 
         [0063]    For this purpose, the invention also provides an expression vector, comprising a nucleic acid according to the invention operably linked to a promoter. And, the invention also provides a host cell, preferably an  E. coli  cell or a  Bacillus subtilis  cell, comprising a nucleic acid coding for a protein according to the present invention, wherein the host cell preferably is transformed with an expression vector of the present invention. The expression vector in the host cell may be separate to or—preferably stably—inserted into the genome of the host cell. 
         [0064]    Such biotechnological protein production by recombinant gene expression also offers the possibility of adding N-terminal and/or C-terminal tags to the protein. Such tags comprise tags as e.g. His-tags or Strep-tags or other tags and are well known to the skilled persons. A particular advantage of such tags is easy purification of the respective protein using specific affinity chromatography systems. These purification protocols are well known to skilled persons. Purification of proteins with His-tags on resins functionalized with Ni-NTA or Ni-IDA is of particular advantage, as such resins are easily available (e.g. from GE Healthcare, Uppsala, Sweden). Another advantage of His-tags attached to proteins of this invention is the non-interference of the His-tag with the enzymatic activity of the enzyme and its use according to this invention. So, such a purification tag might be used to assist protein purification, in case it would be beneficial. 
         [0065]    On the other hand, it is known to the skilled person that such tags might interfere with protein production efficiency and/or specific enzyme activity. As seen in  FIG. 35 , this happened here as well: total enzyme activity in the cell culture for the His-tagged protein is lower than for the protein without His-tag. 
         [0066]    This offers a particular advantageous possibility of either producing larger amounts of protein for larger demands, as for large numbers of tests (e.g. for screening of large numbers of potential inhibitors) or the production of purified protein for detailed biochemical tests (as e.g. determination of enzyme kinetics, inhibitor binding constants etc.) 
         [0067]    In view of the above problem of the present invention, there is also provided a malodour standard composition. The malodour standard composition of the present invention comprises a protein of the present invention, preferably an isolated or purified protein, further preferably comprising or consisting of an amino acid sequence according to any of SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35, together with a substance cleavable by the protein to generate a malodorous product. The cleavable substance may be an ingredient of natural, fresh and sterilized human sweat. According to the present invention, malodour standard compositions are particularly preferred wherein the cleavable substance is N-alpha-lauroyl-L-glutamine. 
         [0068]    The malodour standard compositions of the present invention are particularly useful for generating a strong and typical malodour of human sweat when being brought into contact with fresh and, prior to said contact, essentially odourless human sweat. A particular advantage of such malodour standard compositions according to the present invention is that they are not dependent upon the presence of zinc ions in the malodour standard composition or in sweat. The malodour standard compositions of the present invention thus allow to study and influence the generation of a very typical malodour of human sweat under reproducible conditions, substantially eliminating factors like varying skin surface or sweat temperatures of test persons. 
         [0069]    The malodour standard compositions according to the present invention are particularly suitable for finding and testing the efficacy of substances influencing the generation, the intensity and the “flavour” of sweat malodour. This can be achieved by adding a candidate substance for modifying the speed, intensity or “flavour” of sweat malodour to a malodour standard composition of the present invention which is then brought into contact with human sweat, particularly with fresh and preferably sterilised human sweat. Also, the candidate substance can be added to sweat, particularly fresh and preferably sterilised sweat which is then brought into contact with a malodour standard composition of the present invention. 
         [0070]    The malodour standard composition according to the present invention is not limited to the above described malodour standard compositions. The malodour standard composition can also comprise an isolated protein comprising an amino acid sequence having 
         [0071]    a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98% and/or 
         [0072]    b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99%, 
         [0073]    to an amino acid sequence according to SEQ ID NO:1, wherein sequence identity and sequence similarity are computed according to the EMBOSS needle algorithm having a Gap Open penalty of 10.0, a Gap Extent penalty of 0.5 and using the Blosum62 matrix. The amino acid sequence SEQ ID NO:1 is known from Bacillus subtilis. However, it was not known that such protein, when brought into contact with odourless human sweat, is capable of producing a typical and intense sweat malodour. The protein is thus also useful in malodour standard compositions of the present invention. 
         [0074]    The malodour standard composition of the present invention preferably comprises a protein comprising or consisting of an amino acid sequence according to any of SEQ ID NO:1 to 31, SEQ ID NO:34, OR SEQ ID NO:35, preferably comprising or consisting of an amino acid sequence according to SEQ ID NO:2 or any of SEQ ID NO:5 to 31, SEQ ID NO:34, OR SEQ ID NO:35. Particularly preferred are such malodour standard compositions wherein the protein for generating sweat malodour consists of a purified protein consisting of any of amino acid sequences SEQ ID NO:1 to 31, SEQ ID NO:34, or SEQ ID NO:35, particularly preferably SEQ ID NO:2 or 5 to 31, and most preferably of SEQ ID NO:2. 
         [0075]    Thus, according to the present invention there is provided a malodour standard composition consisting of
       an isolated or purified protein consisting any of the amino acid sequences SEQ ID NO:1, SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35   N-alpha-lauroyl-L-glutamine   and a carrier.       
 
         [0079]    The carrier preferably is a liquid carrier and most preferably is a water buffer adjusted to a pH of &gt;4, even more preferably of 5 to 9 and most preferably of 6,2 to 7,8. It is particularly preferred that such buffer is a buffer made of water, 50 mM NaH 2 PO 4 /K 2 HPO 4  and 50 mM NaCl. Such carrier is easy to produce reproducibly and insufficient quantities. 
         [0080]    According to the invention, there is also provided a malodour inhibition composition. The malodour inhibition composition comprises a malodour standard composition according to the present invention and a potential inhibitor of the cleavage reaction to generate a malodorous product such malodour inhibition composition of the present invention allows to test easily and reproducibly in a standardized way the efficacy of a potential sweat malodour in inhibitor. 
         [0081]    According to the invention, the malodour inhibition composition therefore comprises
       a preferably isolated or purified protein comprising or consisting of an amino acid sequence according to any of SEQ ID NO:1, SEQ ID NO:2 to 31, SEQ ID NO:34, or SEQ ID NO:35,   N-alpha-lauroyl-L-glutamine and   a carrier for allowing the cleavage of N-alpha-L-lauroyl-L-glutamine by the protein in the absence of an inhibitor, and   the candidate inhibitor.       
 
         [0086]    Even more preferably, the malodour inhibitor composition of the present invention consists of
       an isolated or purified protein consisting of the amino acid sequence according to any of SEQ ID NO:1, SEQ ID NO:2, or SEQ ID NO:5 to 31,   N-alpha-lauroyl-L-glutamine,   a carrier for allowing the cleavage of N-alpha-L-lauroyl-L-glutamine by the protein in the absence of an inhibitor, and   a candidate inhibitor.       
 
         [0091]    In the malodour inhibition composition of the present invention, the carrier preferably is a solution, in water, of 50 mM NaCl and 50 mM NaH 2 PO 4 /K 2 HPO 4  at pH 7. 
         [0092]    The present invention further provides a malodour inhibitor screening system, comprising a—preferably isolated—protein comprising an amino acid sequence having
       a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98%, and/or   b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99%,       
 
         [0095]    to an amino acid sequence according to any of SEQ ID NO:1 to 31, SEQ ID NO:34, or SEQ ID NO:35, wherein the sequence identity and sequence similarity are computed according to the EMBOSS needle algorithm having a Gap Open penalty of 10,0, a Gap Extend penalty of 0,5 and using the Blosum62 matrix,
       together with a substance cleavable by the protein to generate a malodorous product under conditions allowing such cleavage, and   a set of inhibitor candidate substances to be screened.       
 
         [0098]    The malodour inhibitor screening system thus preferably comprises a machine performing the steps of reacting the protein and the cleavable substance in the presence of a selected inhibitor candidate substance under conditions which, in the absence of an effective inhibitor, allow the cleavage of the cleavable substance to generate a malodorous product. 
         [0099]    Again, the cleavable substance preferably is N-alpha-lauroyl-L-glutamine. Also for the benefits discussed above the protein preferably is an isolated or purified protein. 
         [0100]    Particularly preferred is a malodour inhibitor screening system of the present invention, wherein the protein is an isolated or purified protein consisting of an amino acid sequence according to any of SEQ ID NO:1, 2 to 31, SEQ ID NO:34, or SEQ ID NO:35 and most preferably is a purified protein consisting of an amino acid sequence according to SEQ ID NO:2. 
         [0101]    The conditions allowing such cleavage include preferably the presence of a water buffer comprising 50 mM NaCl and 50 mM NaH 2 PO 4 /K 2 HPO 4  at pH 7. 
         [0102]    In summary, a malodour inhibitor screening system is particularly preferred which comprises
       a purified protein consisting of the amino acid sequence according to any of SEQ ID NO:1, SEQ ID NO:2, or SEQ ID NO:3 to 31, SEQ ID NO:34, or SEQ ID NO:35,   N-alpha-lauroyl-L-glutamine,   a water buffer of 50 mM NaCl and 50 mM NaH 2 PO 4 /K 2 HPO 4  at pH 7,   an array of inhibitor candidate substances, and   an automat for mixing the protein, N-alpha-lauroyl-L-glutamine and one or more inhibitor candidate substances into the buffer.       
 
         [0108]    Such malodour inhibitor screening system is particularly adapted to be used in high throughput screening applications for testing the efficacy of a large assortment of potential inhibitor substances in varying concentrations. The malodour inhibitor screening system of the present invention thus advantageously aids in the identification of further useful sweat malodour inhibitors. The system further realizes the advantages involved with the protein and malodour standard composition of the present invention, particularly that themalodour generation is independent of zinc ions. 
         [0109]    Again, the formation of malodour and the inhibition of malodour formation can be analysed and quantified by an expert panel as indicated above. Also preferred and particularly useful in high throughput applications, however, is a system according to the present invention wherein the substance to be cleaved and/or a product of such cleavage reaction is detected automatically, e.g. by gas chromatography or optically via photometry, fluorescence photometry or luminescence-photometry upon addition of further reactants. Such means for detection are known to the skilled person, e.g. from example 8 of EP 1387891 B1. 
         [0110]    Accordingly, the present invention also provides for a standardizable method of generating a malodour, comprising the step of reacting a protein comprising or consisting of an amino acid sequence having 
         [0111]    a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98%, and/or 
         [0112]    b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99%, 
         [0113]    to an amino acid sequence according to any of SEQ ID NO:1 to 31, SEQ ID NO:34, or SEQ ID NO:35, wherein the sequence identity and sequence similarity are computed according to the EMBOSS needle algorithm having a Gap Open penalty of 10.0, a Gap Extend penalty of 0.5 and using the Blosum62 matrix,
       with a substance cleavable by this protein under conditions allowing such cleavage to produce a malodour, wherein the substance preferably is N-alpha-lauroyl-L-glutamine.       
 
         [0115]    The method is preferably performed in fresh and sterilised human sweat, or in a water buffer of 50 mM NaCl and 50 mM NaH 2 PO 4 /K 2 HPO 4  buffer at pH 7. 
         [0116]    The protein preferably consists of an amino acid sequence according to any of SEQ ID NO:1 to 31, SEQ ID NO:34, or SEQ ID NO:35, preferably according to any of SEQ ID NO:1, SEQ ID NO:2, or SEQ ID NO:5 to 31 and most preferably according to SEQ ID NO:2. 
         [0117]    Further, the invention provides a method of screening for malodour inhibitors the method comprises the steps of 
         [0118]    1. incubating a protein comprising an amino acid sequence having 
         [0119]    a) a sequence identity of at least 93%, preferably at least 95%, more preferably of at least 98%, and/or 
         [0120]    b) a sequence similarity of at least 97%, preferably at least 98%, more preferably of at least 99%, 
         [0121]    to an amino acid sequence according to any of SEQ ID NO:1 to 31, SEQ ID NO:34, or SEQ ID NO: 35, wherein the sequence identity and sequence similarity are computed according to the EMBOSS needle algorithm having a Gap Open penalty of 10,0, a Gap Extend penalty of 0,5 and using the Blosum62 matrix,
       together with a substance cleavable by the protein under conditions allowing for such cleavage reaction in the absence of in inhibitor and   an inhibitor candidate substance for potentially inhibiting the cleavage reaction, and       
 
         [0124]    2. measuring malodour generation. 
         [0125]    The invention is further described by reference to the examples and figures. These examples are not to be understood to limit the scope of the claims. 
       EXAMPLES 
     Example 1 
     Amplification of the yxel Gene by PCR and Cloning into  E. Coli  Expression Vectors 
       [0126]    Genomic DNA of a Bacillus subtilis strain, isolated from human armpit was used as template for PCR amplification. The primers Forward (5′-GGGACTGATCATATGTGCACAAGTCTTAC-3′), (SEQ ID NO:36), and Reverse (5′-ATTGAGGATCCTTAATTAAGCTCATGAATACTCT-3′), (SEQ ID NO:37), were used for PCR amplification. 
         [0127]    The resulting PCR-product was treated with restriction endonucleases Ndel and BamHI (New England Biolabs, Frankfurt, Germany) according to instructions of the manufacturer and cloned into plasmids pET24a (Merck, Darmstadt, Germany) and pET28a (Merck, Darmstadt, Germany). The resulting expression vectors were called pET24a::yxel or pET28a::yxel. They contain a nucleic acid coding for a protein of SEQ ID NO 1. In vector pET28a, the protein is linked to a His-Tag of 6 consecutive histidine amino acids. 
       Example 2 
     Gene Expression and Protein Production in  E. Coli    
       [0128]      E. coli  BL21(DE3) was used as expression host. The strains (either without plasmid or carrying the expression vectors described in Example 1) were grown at 37° C. in 100 ml Luria-Bertani medium using 250 ml shake flasks with vigourous shaking. Plasmid-containing strains were grown in presence of Luria-Bertani medium containing 30 mg/l kanamycin. After the cell density reached an OD600 of 1, IPTG was added to a final concentration of 0.1 mM, followed by additional incubation under identical conditions for another 2 hours. 
         [0129]    1.5 ml samples were taken from the cultures, cells were harvested by centrifugation and analyzed by SDS-PAGE followed by Coomasie staining. Strong gene expression and protein production was observed after induction, as shown by  FIG. 34 . 
       Example 3 
     Determination of Enzyme Activity and Test for Inhibitors Effects 
       [0130]    Cells obtained as in example 2 were harvested by centrifugation and washed twice with PBS buffer to remove residual medium components. The final cell pellet was resuspended in PBS buffer (per litre water: 8 g NaCl, 0.2 g KCl, 1.44 g Na 2  HPO 4 , 0.24 g K H 2 PO 4 , pH 7.4) to reach a final OD600 of 30. This cell suspension of strains (either without plasmid or carrying the expression vectors described in Example 1) was used for the activity tests. The washed cell suspensions were contacted in PBS buffer with N-alpha-lauryl-glutamin (0.2 mg/ml final concentration, “LG” in  FIG. 35 ), at 37° (final volume 0.25 ml) for 15 min. The actual test was performed as described in example 7 of WO 02/092024 A2, with GC as the test method. The plasmid-free strain showed some background activity, whereas the strains carrying the expression vectors showed strong enzyme activity, as can be seen in  FIG. 35 . This figure displays the enzyme activity relative to the activity of the enzyme of the present invention expressed in pET 24a. As a side note, contacting this enzyme with fresh human sweat results in development of an intense smell of human sweat. 
         [0131]    As a test for inhibition of the activity, sodium acetate was added to one set of samples to a final concentration of 100 mM. As a result, the enzyme activity was inhibited to the level of the background activity of the plasmid-free  E. coli  strain. 
         [0132]    The assay was repeated with enzymes having an amino acid sequence according to SEQ ID NO:2, and SEQ ID NO:5 to 31, respectively. All enzymes likewise produced an intense smell of human sweat when brought into contact with fresh, odorless human sweat.