Vitamin K functions as a cofactor for the enzyme, γ-glutamylcarboxylase (GGCX), which catalyzes the carboxylation of the amino acid glutamic acid (Glu) to γ-carboxyglutamic acid (Gla). Vitamin K-dependent γ-carboxylation that occurs only on specific glutamic acid residues in identified vitamin K-dependent proteins (VKDP) is critical for their ability to bind calcium