Formation of -cyanoalanine by O-acetylserine sulfhydrylase

Cell-free extracts of Bacillus megaterium form beta-cyanoalanine (beta-CNA)-(14)C from Na(14)CN and l-cysteine, O-acetyl-l-serine or, to a lesser extent, l-serine. However, the presence of cyanide in the growth medium does not increase the capacity of cell extracts to catalyze the formation of beta-CNA from cysteine and cyanide. The formation of beta-CNA is readily detected in extracts of cells grown in synthetic media with sulfate or l-djenkolic acid as sulfur sources; such cells also exhibit an increased ability to form cysteine when compared with cells grown on cysteine as the sulfur source. beta-CNA formation could not be detected in extracts of cells grown on cysteine as the sulfur source. A 40-fold purification of the O-acetyl-serine sulfhydrylase resulted in the co-purification of the beta-CNA-forming activity. The sulfhydrylase and the beta-CNA-forming activity co-chromatographed on diethyl-aminoethyl cellulose and Sephadex G-100.