vitamin K-dependent clotting factor

vitamin K-dependent clotting factor

Any of a group of coagulation factor proenzymes (factors II, VII, IX and X) produced in the liver that contain multiple residues of gamma-carboxyglutamic acid, an amino acid produced by the post-translational action of a vitamin K-dependent gamma-carboxylase on certain glutamyl residues.
 
Four other proteins have gamma-carboxyglutamic acid, and have been designated proteins C, S, Z and M; while M is poorly characterised, proteins C, S and Z have amino-terminal homology with prothrombin. Vitamin K-dependent clotting factors also have another unusual amino acid, aspartic acid.
References in periodicals archive ?
(28) Another such protein is des-carboxy-prothrombin (PIVKA-II), the undercarboxylated forms of prothrombin, a vitamin K-dependent clotting factor synthesized in the liver.
One reason is that, unlike osteocalcin in bone, in the average healthy population clotting factors in the liver are fully carboxylated: "The vitamin K-dependent clotting factors are all produced in the liver and, in contrast to osteocalcin, they are all fully carboxylated in the healthy population."
A study using vitamin K1 (150 [micro]gm phytomenadione) daily in patients with unstable anticoagulation control showed that increasing and stabilizing the body's stores of the vitamin allowed for better control of anticoagulation by maintaining steady activation of vitamin K-dependent clotting factors [46].
The differential diagnosis includes dysfibrinogenemia, prothrombin deficiency, factor V deficiency, combined deficiency of factors V and VIII (F5F8D), factor X deficiency, and hereditary combined deficiency of the vitamin K-dependent clotting factors. All of these conditions feature prolongation of both the PT and the aPTT (1).
(2) Superwarfarin exposure must be included in the differential diagnosis when a patient presents with deficiency of vitamin K-dependent clotting factors and has a limited response to vitamin K supplementation.
Reduced vitamin K is a necessary cofactor in the gamma carboxylation of the 4 vitamin K-dependent clotting factors: factors II, VII, IX, X.
These are more sensitive to a reduction in vitamin K-dependent clotting factors than are the rabbit brain thromboplastins commonly used on this continent.