Selenol-catalyzed reduction of disulfide bonds in peptides and proteins

Abstract

This chapter measures the kinetics of selenol-catalyzed reduction of disulfide bonds in proteins and in small organic disulfides using dithiothreitol (DTT) and sodium borohydride as reductants. Disulfide-reducing reagents are used in biochemistry to reduce the disulfide bonds in proteins and peptides and to maintain the essential thiol groups in proteins by preventing their oxidation to the disulfide state. Selenols and their precursors catalyze the interchange reactions of organic dithiols and disulfides. The rates of activation of sulfhydryl enzymes by cysteine are accelerated using excess selenocystine. Selenocystamine, a commercially available diselenide, is used as the precursor of the catalyst and is reduced to its selenol (selenocysteamine) in situ . The rate determining step is identified in the selenol-catalyzed reduction of disulfide as the reaction of selenolate anion with disulfide. The chapter also describes the practical conditions using selenocystamine and DTT to achieve rapid reductions of disulfide bonds in proteins.