In animals, vitamin K2 carboxylates glutamate residues in certain proteins, to give carboxyglutamate. This modification allows the protein to bind calcium, an essential event in the blood clotting cascade. Carboxylation of glutamate residues occurs in other proteins that are active in the mobilization or transport of calcium.

Vitamin K is found in plants as phylloquinone (vitamin K1) and in animals as menaquinone (vitamin K2). Vitamin K2 is essential for the carboxylation of glutamate residues in certain proteins, to give -carboxyglutamate. This modification allows the protein to bind calcium, an essential event in the blood clotting cascade. Carboxylation of glutamate is also important in other proteins involved in the mobilization or transport of calcium.