chapter  5
40 Pages

Vitamin K-Dependent Proteins

WithJohn W. Suttie

The vitamin K-dependent plasma clotting factors are components of a complex system of proteins whose function is that of normal hemostasis, the absence of either a hemorrhagic or thrombotic event. The vitamin K-dependent plasma proteins are a group of structurally related glycoproteins that represent less than 0.5% of the total plasma protein pool. Patients being treated for hemophilia with plasma-derived F VIII or F IX concentrations often develop antibodies to these proteins, which inhibit the activity of the infused proteins and have an increased risk of viral transmission. Osteocalcin is readily solubilized when bone powder is extracted in the presence of chelating agents, but early studies of this protein indicated that it was not the only protein present in bone, and that substantial amounts of non-osteocalcin Gla were also found in cartilage. Proteins containing Gla residues have also been found in the venom of poisonous snakes.