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Biochemistry

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Vitamins, Harmones and Hemoglobin

Question
30 out of 30
 

Vitamin K is required for(AIIMS May 2007)



A Carboxylation
B Hydroxylation

C Acetylation
D Sulfuration

Ans. A Carboxylation

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.

Vitamins, Harmones and Hemoglobin Flashcard List

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