Document Detail


A hydrolase from Lactobacillus sakei moonlights as a transaminase.
MedLine Citation:
PMID:  23354716     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Enzymatic transamination of amino acids yields α-keto acids and is the initial step for the production of volatile compounds that contribute to the sensory perception of fermented foods such as salami. Lactobacillus sakei is one of the lactic acid bacterial strains commonly used in starter cultures. Although the genome sequence of L. sakei 23K lacks genes encoding typical branched-chain amino acid transaminases, transamination activity and the formation of amino acid-derived volatile metabolites could be demonstrated. A protein purified from L. sakei is held responsible for the transamination activity. By heterologous expression of the corresponding gene in Escherichia coli, we were able to characterize the transamination side activity of an enzyme annotated as a putative acylphosphatase (AcP). A transamination side activity of hen egg white lysozyme (HEWL) was also discovered. Both enzymes showed substrate specificity toward branched-chain and aromatic amino acids. AcP also accepted l-methionine. Activity was optimal at neutral pH for both enzymes, whereas AcP showed a significantly higher temperature optimum (55°C) than that of HEWL (37°C). Kinetic parameters revealed high affinity toward l-leucine for AcP (K(m) = 1.85 mM) and toward l-isoleucine for HEWL (K(m) = 3.79 mM). AcP seems to play a major role in the metabolism of amino acids in L. sakei.
Authors:
Quirin Sinz; Simone Freiding; Rudi F Vogel; Wilfried Schwab
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-01-25
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  79     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2013 Apr 
Date Detail:
Created Date:  2013-03-15     Completed Date:  2013-08-28     Revised Date:  2013-10-08    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2284-93     Citation Subset:  IM    
Affiliation:
Biotechnology of Natural Products, Technische Universität München, Freising, Germany.
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MeSH Terms
Descriptor/Qualifier:
Acid Anhydride Hydrolases / chemistry,  genetics,  metabolism*
Cloning, Molecular
Enzyme Stability
Escherichia coli / genetics
Gene Expression
Hydrogen-Ion Concentration
Kinetics
Lactobacillus / enzymology*,  genetics
Leucine / metabolism
Muramidase / metabolism
Substrate Specificity
Temperature
Transaminases / chemistry,  genetics,  metabolism*
Chemical
Reg. No./Substance:
61-90-5/Leucine; EC 2.6.1.-/Transaminases; EC 3.2.1.-/hen egg lysozyme; EC 3.2.1.17/Muramidase; EC 3.6.-/Acid Anhydride Hydrolases; EC 3.6.1.7/acylphosphatase
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