Dissimilation of Methionine by Achromobacter starkeyi

Methionine was decomposed by some bacteria which were isolated from soil. The sulfur of the methionine was liberated as methanethiol, and part of this became oxidized to dimethyl disulfide. Detailed studies with one of these cultures, Achromobacter starkeyi, indicated that the first step in methionine decomposition was its oxidadative deamination to alpha-keto-gamma-methyl mercaptobutyrate by a constitutive amino acid oxidase. The following steps were carried out by inducible enzymes, the synthesis of which was inhibited by chloramphenicol. alpha-Keto-gamma-methyl mercaptobutyrate was split producing methanethiol and alpha-keto butyrate which was oxidized to propionate. The metabolism of propionate was similar to that described for animal tissues; the propionate was carboxylated to succinate via methyl malonyl coenzyme A, and the succinate was metabolized through the Krebs cycle.