New strains of microorganisms that produce 2-amino-4-alkylthio-butyric acid, useful for preparing L-methionine, from simple carbon source and a mercaptan or its salt, have modified methionine synthase activity

摘要

Strain (A) of a microorganism which produces a 2-amino-4-alkylthio-butyric acid (I) by metabolizing a simple sugar and a thiol (II), or its salt, and has at least one gene encoding an enzyme with modified methionine synthase (MS) activity. Strain (A) of a microorganism which produces a 2-amino-4-alkylthio-butyric acid of formula (I) RS-(CH 2) 2-CHNH 2-COOH (I) by metabolizing a simple sugar and a thiol (II), R'-SH, or its salt, and has at least one gene encoding an enzyme with modified methionine synthase (MS) activity. R : 1-8C linear or branched alkyl, optionally substituted by one or more hydroxy or by (hetero)aryl with one or more nitrogen or sulfur atoms in the ring, i.e. phenyl, pyridyl, pyrroly, pyrazolyl, triazolyl, tetrazolyl, thiazolyl or thienyl; R' : hydrogen or as R. Independent claims are also included for the following: (1) modified cystathioninegamma -synthase (X) having MS activity; (2) nucleic acid (NA) that encodes (X); (3) cloning and/or expression vector containing (NA) and elements for regulating expression and transcription of (X); (4) method of screening for a bacterial strain that has a gene encoding (X) or an acylhomoserine sulfhydrylase (Y), for preparation of (A); and (5) method for producing (I) by culturing (A) or by using MS activity present in activated bacteria or their extracts.