Vitamin K-dependent carboxylase. Demonstration of a vitamin K- and O2-dependent exchange of 3H from 3H2O into glutamic acid residues.

The rat liver vitamin K-dependent carboxylase has been studied with t-butoxycarbonyl-Glu-Glu-Leu-OMe as a substrate. The crude enzyme preparation catalyzes incorporation of 3H from media 3H2O into the glutamic acid residues of the substrate. This incorporation is dependent on vitamin KH2 and O2, is stimulated by NaCN, and is inhibited by increasing the HCO3- concentration. These data lend support to an enzymatic mechanism involving a vitamin K- and O2-dependent formation of a carbanion at the gamma-position of the glutamic acid residue followed by attack of CO2 to form gamma-carboxyglutamic acid.