Purification and characterization of l-serine transacetylase and [formula omitted] sulfhydrylase from kidney bean seedlings ( Phaseolus vulgaris)

Abstract

1. 1. Serine transacetylase and O-acetylserine sulfhydrylase have been purified over 50-fold from kidney bean seedlings ( Phaseolus vulgaris) by ammonium sulfate precipitation, and chromatography on DEAE-cellulose and Agarose gel filtration. Each enzyme was free of the other. 2. 2. Serine transacetylase has a pH optimum of 8.25–8.5, is specific for serine and is inhibited by sulfhydryl reagents and l-cysteine. The calculated K m ′s for serine and acetyl-CoA were 6 · 10 −4M and 2 · 10 −4M, respectively. 3. 3. O-Acetylserine sulfhydrylase has a broad pH optimum (7.5–8.5). In addition to the synthesis of cysteine, it catalyzes the formation of S-methylcysteine from methylmercaptan and O-acetylserine. No requirement for pyridoxal phosphate could be demonstrated, though it would be expected to be a cofactor.