All of the following are required for hydroxylation of proline residues except:

Ans. B. GlutamateProline is an imino acid. It undergoes hydroxylation to form collagen in the body. It is the principal residue in proteins to be hydroxylated. Hydroxylation is the process of attachment of hydroxyl group in the presence of large, multi-subunit enzymes prolyl 4-hydroxylase, prolyl 3-hydroxylase and lysyl 5-hydroxylase, respectively. These reactions require iron (as well as molecular oxygen and a-ketoglutarate) to carry out the oxidation, and use ascorbic acid (vitamin C) to return the iron to its oxidized state. Deprivation of ascorbate leads to deficiencies in proline hydroxylation, which leads to less stable collagen, which can manifest itself as the disease scurvy.