MCQ 41 Vitamin K is required for:

A.Hydroxylation
B.Chelation
C.Transamination
D.Carboxylation

The correct answer is : D.Carboxylation

NOTE: The only known biological role of vitamin K is as a cofactor for an enzyme carboxylase that catalyzes carboxylation of glutamic acid residues on vitamin K-dependent proteins include:

• Coagulation proteins: factors II (prothrombin),VII,IX and X
• Anticoagulation proteins: Protein C,S and Z
• Bone proteins: osteocalcin and matrix-Gla protein
• Gas6 is a vitamin K-dependent protein that is found throughout the nervous system,as well in the heart,lungs,stomach,kidneys,and cartilage.
• Carboxylation of glutamic acid residues is critical for the calcium-binding function of those proteins.