Regulatory Properties of l-Methionine Biosynthesis in Obligate Methylotroph OM 33: Role of Homoserine-O-transsuccinylase

Abstract

A cell-free extract of obligate methylotroph strain OM 33 catalyzed the formation of O-succinyl-L-homoserine from L-homoserine and succinyl-CoA, while the corresponding homoserine derivative from acetyl-CoA was scarcely formed. These results indicate that the acylation of L-homoserine, the initial step of L-methionine biosynthesis, was catalyzed by homoserine-O-transsuccinylase. In this bacterium, homoserine-O-transsuccinylase was subject to strict feedback inhibition by S-adenosyl-L-methionine (SAM). On the other hand, the enzyme of an ethionine-resistant mutant OE 120 derived from strain OM 33, was scarcely affected by SAM. These observations suggest the important role of homoserine-O-transsuccinylase in the biosynthesis of l-methionine.