SYNTHESIS OF BIOLOGICALLY ACTIVE SELENIUM-CONTAINING AMINO ACIDS AND PEPTIDES

Abstract

Abstract We here describe the synthesis of selenium amino acids with O-acetylhomoserine sulfhydrylase, partially purified from baker's yeast. The enzyme was found to catalyze the syntheses of L-selenocystine and L-selenohomocystine from sodium diselenide with the corresponding acetyl-derivatives of serine and homoserine, respectively. L-Serine O-sulfate also serves as a substrate of the β-replacement reaction. Sodium diselenide is less efficient as a substituent donor than the physiological substrate, sodium sulfide and inhibits the enzyme at high concentrations. Therefore, limited amounts of sodium diselenide were added to the reaction mixture to increase the yield (about 60%). This provides a facile method to produce optically active seleno-cystine and selenohomocystine. In addition, we developed a convenient method for the synthesis of a new selenium-containing amino acid, L-selenodjenkolic acid (3,3′-methyl-enediselenobis(2-amino-propionic acid)) from L-selenocystine thus prepared. This amino acid undergoes α,β-elimination to produce pyruvate, formaldehyde, ammonia and selenium by bacterial methionine γ-lyase under aerobic conditions.