Evidence for the glycoprotein nature of vitamin K-dependent carboxylase from rat liver.

The ability of the rat liver microsomal vitamin K-dependent carboxylase and microsomal precursors of prothrombin and other vitamin K-dependent proteins to bind to lectin gels has been determined. Under denaturing conditions which dissociate precursor substrates from the carboxylase enzyme, prothrombin precursors and microsomal proteins labeled in gamma-carboxyglutamate residues with [14C]bicarbonate were nearly quantitatively bound to concanavalin A gels. When lentil lectin gels were used, only about one third of these proteins were bound, suggesting a heterogeneity of this glycoprotein pool. Under non-denaturing conditions, both precursor proteins and vitamin K-dependent carboxylase activity were retained on either concanavalin A or lentil lectin gels. These data are consistent with an increase in lectin binding determinants in the precursor-carboxylase complex and are evidence for the glycoprotein nature of this microsomal enzyme.