Open AccessYtjE from Lactococcus lactis IL1403 Is a C-S Lyase with α,γ-Elimination Activity toward Methionine
Author(s) -
M. Carmen Martínez-Cuesta,
Carmen Peláez,
John Eagles,
Michael J. Gasson,
Teresa Requena,
Seán Hanniffy
Publication year - 2006
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.00712-06
Subject(s) - lactococcus lactis , dimethyl trisulfide , methanethiol , methionine , cheese ripening , biochemistry , cysteine , escherichia coli , cystathionine beta synthase , chemistry , dimethyl disulfide , lyase , thiol , enzyme , recombinant dna , biology , sulfur , amino acid , bacteria , ripening , food science , organic chemistry , gene , lactic acid , genetics
Cheese microbiota and the enzymatic conversion of methionine to volatile sulfur compounds (VSCs) are important factors in flavor formation during cheese ripening and the foci in biotechnological approaches to flavor improvement. The product ofytjE ofLactococcus lactis IL1403, suggested to be a methionine-specific aminotransferase based on genome sequence analysis, was therefore investigated for its role in methionine catabolism. TheytjE gene fromLactococcus lactis IL1403 was cloned inEscherichia coli and overexpressed and purified as a recombinant protein. When tested, the YtjE protein did not exhibit a specific methionine aminotransferase activity. Instead, YtjE exhibited C-S lyase activity and shared homology with the MalY/PatC family of enzymes involved in the degradation ofl -cysteine,l -cystine, andl -cystathionine. YtjE was also shown to exhibit α,γ-elimination activity towardl -methionine. In addition, gas chromatographic-mass spectrometry analysis showed that YtjE activity resulted in the formation of H2 S froml -cysteine and methanethiol (and its oxidized derivatives dimethyl disulfide and dimethyl trisulfide) froml -methionine. Given their significance in cheese flavor development, VSC production by YtjE could offer an additional approach for the development of cultures with optimized aromatic properties.