Synthesis of selenocystine and selenohomocystine with O-acetylhomoserine sulfhydrylase.

Abstract

We describe here the synthesis of selenium amino acids with O-acetylhomoserine sulfhydrylase, partially purified from baker’s yeast. The enzyme was found to catalyze the synthesis of l-selenocystine and l-selenohomocystine from Na2Se2 with the corresponding acetyl-derivatives of serine and homoserine, respectively. l-Serine-O-sulfate also serves as a substrate of the β-replacement reaction. Na2Se2 is less efficient as a substituent donor than the physiological substrate, NaHS, and inhibits the enzyme at high concentrations. Therefore, limited amounts of Na2Se2 were added to the reaction mixture to increase the yield (50 to 60%). This provides a facile method to produce optically active selenocystine and selenohomocystine.