MGP, also known as Matrix Gla protein, is a protein involved in regulating calcification in the extracellular matrix, in particular in cartilage and arteries. MGP is a vitamin K-dependent protein, and contains five to six residues of Gla, a Ca2+ binding amino acid requiring vitamin K-dependent gamma carboxylase for its formation. It is found in human bone extracts, likely formed by COOH-terminal processing by carboxypeptidase Blike enzymatic activity.