Formation of β-Cyanoalanine by O -Acetylserine Sulfhydrylase

Abstract

Cell-free extracts of Bacillus megaterium form β-cyanoalanine (β-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 β-CNA from cysteine and cyanide. The formation of β-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. β-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 β-CNA-forming activity. The sulfhydrylase and the β-CNA-forming activity co-chromatographed on diethyl-aminoethyl cellulose and Sephadex G-100.