METHOD FOR THE ENZYMATIC PRODUCTION OF ALPHA-KETOBUTYRATE

摘要

This invention relates to a process for the enzymatic production of a-ketobutyrate and its derivatives, in particular isoleucine. In the described process a-ketobutyrate is obtained from activated homoserine by ?-elimination. Homoserine is activated to either acylhomoserine or phosphohomoserine using homoserinetransacylase and homoserine kinase, respectively. Subsequently phosphohomoserine and/or acylhomoserine is/are transformed into phosphate or/and acylate, ammonia and a-ketobutyrate through the ?-eliminase activity of cystathionine- ?-synthase and/or acylhomoserine sulfliydrylase and/or phosphohomoserine sulfhydrylase. This reaction is favored by (i) reducing intracellular concentrations of H2S or cysteine, (ii) reducing the access of these two sulfur containing substrates to the enzyme cystathionine-?- synthase and/or acylhomoserine sulfhydrylase and/or phosphohomoserine sulfliydrylase or (iii) by using cystathionine-?-synthase and/or acylhomoserine sulfliydrylase and/or phosphohomoserine sulfhydrylase with high ?-elimination and low cystathionine-?-synthase and/or low acylhomoserine sulfliydrylase and/or low phosphohomoserine sulfhydrylase activity. At least one of these measures is applied in microorganisms, in particular coryneform bacteria and enterobacteria, in which as a consequence a-ketobutyrate and/or its derivatives can be produced in high quantities.