Peroxide Bond Cleavage in the Dianions of Peroxy-bis-nols : a Computational Study

Abstract

The vitamin K-dependend g-glutamyl carboxylase carries out a unique post-translational modification of proteins that involves the insertion of a molecule of carbon dioxide into the g position of Glu side chains, converting them to Gla residues. This reaction, which is highly endothermic, is driven by the strongly exothermic oxidation of the reduced form of vitamin K into vitamin K 2,3-epoxide and water by the base-catalyzed reaction with molecular oxygen. The currently accepted mechanism for this reaction involves the formation of a "super" base, believed to be incompatible with a living cell--free radicals may be involved. The purpose of this study was to test the theory that the dianion of a peroxy-bis-enol may be a critical intermediate in the enzymatic reaction.