Which of the following is/are not a substrate or cofactor for prolyl hydroxylase?

C. Biotin.

E. Copper.

DISCUSSION: Prolyl hydroxylase is one of the rate-limiting enzymes in collagen synthesis. Substrates and cofactors such as iron, alpha-ketoglutarate, ascorbate, and oxygen are important participants in this process. If insufficient prolines are hydroxylated, then the alpha-peptide collagen chains cannot assume a stable triple helix, the collagen cannot be exported from the fibroblasts, and the incomplete, unassociated alpha chains are broken down. Thus, ascorbate deficiency (scurvy) and hypoxia have similar effects on collagen synthesis.