Synthesis of L-cysteine and its analogues by intact cells [Aerobacter aerogenes and A. cloaceae] containing cysteine desulfhydrase

Cysteine desulfhdrase catalyzes β-replacement, the reverse reaction of α,β-elimination, as Well as α,β -elimination. These reactions were studied with intact cells of Aerobacter aerogenes 1-3-2 and Aerobacter cloacae IFO 12009 containing cysteine desulfbydrase. l-Cysteine and its analogues were synthesized by replacement and reverse reactions using intact cells. β -Chloro l-alanine, l-cysteine, S-methyl-l-cysteine, S-allyl-l-cysteine and l-serine were used as substrates together with hydrogen sulfide and methyl mercaptan to synthesize l-cysteine and S-methyl-l-cysteine via replacement reaction by intact cells. l-Cysteine synthesized from β-chloro-l-alanine was confirmed to be entirely in l-form after isolation and identification of the product. The reverse reaction for synthesis of l-cysteine and S-methyl-l-cysteine from hydrogen sulfide or methyl mercaptan, pyruvate and ammonia was also catalyzed by intact cells. β-chloro-l-alanine was found to be the best substrate for synthesis of l-cysteine and S-methyl-l-cysteine by β-replacement reaction.