d‐Cysteine desulfhydrase of Escherichia coli

Abstract

D-Cysteine-specific desulfhydrase is found in some intestinal bacteria. E. coli W3110 .DELTA.trpED 102/F''.DELTA.trpED102 was found to have the highest enzyme activity. The enzyme was purified from E. coli W3110 .DELTA.trpED102/F''.DELTA.trpED102 in six steps. After the last step the enzyme appeared to be homogeneous by the criteria of polyacrylamide gel electrophoresis, analytical ultracentrifugation and double diffusion in agarose. The enzyme has a molecular mass of about 67000 Da and consists of two subunits identical in molecular mass. The enzyme exhibits absorption maxima at 278 nm and 418 nm, which are independent of pH (6.5-10.5), and contains 2 mol pyridoxal phosphate/mol enzyme. The holoenzyme is resolved to the apoenzyme by incubation with phenylhydrazine, and reconstituted on the addition of pyridoxal phosphate. D-Cysteine desulfhydrase also catalyzes the .beta.-replacement reaction of the chlorine of 3-chloro-D-alanine with thioglycolic acid to yield S-carboxymethyl-D-cysteine. Its catalytic and immunological properties are compared with those of 3-chloro-D-alanine dehydrochlorinase.