Vitamin K is required for

Carboxylation The only known biological role of vitamin K is as a cofactor for an enzyme carboxylase that catalyzes carboxylation of glutamic acid residues on vitamin K-dependent proteins. The key vitamin K-dependent proteins include: Coagulation proteins: factors II (prothrombin), VII, IX and X Anticoagulation proteins: proteins C, S and Z Bone proteins: osteocalcin and matrix-Gla protein Gas6 is a vitamin K-dependent protein that is found throughout the nervous system, as well in the hea, lungs, stomach, kidneys, and cailage. These proteins have in common the requirement to be post-translationally modified by carboxylation of glutamic acid residues (forming gamma-carboxyglutamic acid) in order to become biologically active. Prothrombin, for example, has 10 glutamic acids in the amino-terminal region of the protein which are carboxylated. Without vitamin K. the carboxylation does not occur and the proteins that are synthesized are biologically inactive. Carboxylation of glutamic acid residues is critical for the calcium-binding function of those proteins. Also Know There are two naturally occurring forms of vitamin K: - phylloquinone synthesized by plants - menaquinones synthesized by intestinal bacteria Synthetic forms of vitamin K are: - menadiotze - menadiol - menadiol acetate