Vitamin-K Dependent Factors

This term is used to describe, as a group, coagulation factors II, VII, IX, and X (as well as the anti-coagulation factors known as protein C and protein S). All of these factors require the presence of vitamin K in order for the liver to modify some of their glutamic acid residues into a form that makes the whole factor able to serve their purpose (this process is known as “gamma-carboxylation”, and it is a specific modification done by an enzyme that only acts in concert with a form of vitamin K). The Vitamin-K dependent factors have decreased function when a patient is taking medications designed to inhibit gamma-carboxylation (these medications are called “Vitamin-K Antagonists” or “VKAs”, and the most famous of them is warfarin).

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