Abstract
The highly purified protein C component of clostridial glycine reductase is required in addition to seleno-protein A and protein B for the conversion of glycine to acetate and ammonia in the presence of arsenate. As shown by Arkowitz and Abeles [Arkowitz, R. A. & Abeles, R. H. (1989) Biochemistry 28, 4639-4644], the products are ammonia and acetyl phosphate in the presence of phosphate. The protein C component alone catalyzes an arsenate-dependent decomposition of acetyl phosphate, showing that it serves as the acetyl group acceptor in the overall reaction. A thiol-reducing agent and Mg2+ are required for catalysis of the arsenolysis reaction by protein C. Alkylation or heating at 60 degrees C completely abolishes the ability of protein C to catalyze the arsenolysis reaction and to participate as an essential component in the overall glycine reductase reaction.