Matrix Gla protein (MGP) is a potent inhibitor of vascular calcification. MGP is mainly synthesized and expressed in cartilage and the vessel wall, where it is produced by the chondrocytes and vascular smooth muscle cells, respectively. During biosynthesis, MGP undergoes two forms of post-translational modifications: the phosphorylation of 3 serine residues and the γ-carboxylation of 5 glutamate residues. Phosphorylation of MGP is essential for its regular cellular secretion, and the vitamin K-dependent carboxylation is crucial for the calcification inhibitory activity. MGP plays a role in bone metabolism and atherosclerosis.