Vitamins, Harmones and Hemoglobin
Vitamin K is required for(AIIMS May 2007)
a. Generation of biologically active clotting factors involves the post translational modification of glutamate residues to gamma carboxy glutamate by specific vitamin K dependant protein carboxylase.
b. Vitamin K
a. There are two natural forms of vitamin K: vitamin K I, also known as hylloquinone, from vegetable and animal sources, and vitamin K II, or menaquinone, which is synthesized by bacterial flora and found in hepatic tissue. Menadione, or vitamin K III, is a chemically synthesized pro-vitamin that can be converted to menaquinone by the liver.
b. Vitamin K is required for the posttranslational carboxylation of glutamic acid, which is necessary for calcium binding to y-carboxylated proteins such as prothrombin (factor II); factors VII, IX, and X; protein C; protein S; and proteins found in bone (bone gla, matrix gla protein, and osteocalcin). However, the importance of vitamin K for bone mineralization is not known. Warfarin-type drugs inhibit y carboxylation by preventing the conversion of vitamin K to its active hydroquinone form.