Physiological comparison of D-cysteine desulfhydrase of Escherichia coli with 3-chloro-D-alanine dehydrochlorinase of Pseudomonas putida CR 1-1.

D-Cysteine desulfhydrase of Escherichia coli W3110 delta trpED102/F' delta trpED102 was physiologically characterized. It was found to be located in the cytosolic fraction, as 3-chloro-D-alanine dehydrochlorinase is. D-Cysteine desulfhydrase catalyzed not only the alpha, beta-elimination reaction of O-acetyl-D-serine to form pyruvate, acetic acid and ammonia, but also the beta-replacement reaction of O-acetyl-D-serine with sulfide to form D-cysteine. However, these reactions appeared not to proceed in vivo. No other activity of D-cysteine synthesis from O-acetyl-D-serine and sulfide was detected in a crude cell extract of E. coli which was immunotitrated with antibodies raised against the purified D-cysteine desulfhydrase. Although D-cysteine desulfhydrase catalyzes the degradation (alpha, beta-elimination reaction) of 3-chloro-D-alanine, which is an effective antibacterial agent, E. coli W3110 delta trpED102/F' delta trpED102 did not show resistance against 3-chloro-D-alanine. Therefore, D-cysteine desulfhydrase does not contribute to 3-chloro-D-alanine detoxification in vivo.