Biochemistry – Question 5
Vitamin K is needed for which of these post translational modification processes:
a) Methylation
b) Carboxylation
c) Hydroxylation
d) Transketolation
b) Carboxylation
Gamma-glutamyl carboxylase is an enzyme that catalyzes the posttranslational modification of vitamin K-dependent proteins.
Many of these vitamin K-dependent proteins are involved in coagulation so the function of the encoded enzyme is essential for hemostasis.
Important points:
Two proteins that contain gamma carboxyglutamate are present in bone, osteocalcin and bone matric Gla protein.
Osteocalcin also contains hydroxyproline, so its synthesis is dependent on both vitamin K and C; in addition, its synthesis is induced by vitamin-D.
Ref: Harper’s Illustrated Biochemistry, 31st Edition and Page-532-33
