Which vitamin is a cofactor for ALA synthase?

Pyridoxine, known as vitamin B6, serves as a cofactor for the enzyme ALA synthase, which is crucial in the biosynthesis of heme. ALA synthase catalyzes the first step in heme production by condensing glycine and succinyl-CoA to form delta-aminolevulinic acid (ALA). The presence of pyridoxine is essential for this reaction to occur efficiently because it participates in the enzymatic processes through its role in amino acid metabolism.

Vitamin B6 is involved in the transamination and decarboxylation reactions, which are vital for amino acid metabolism as well. A deficiency in vitamin B6 may lead to decreased activity of ALA synthase, subsequently causing disturbances in heme synthesis, potentially leading to conditions like microcytic anemia or sideroblastic anemia due to accumulated precursors.

In contrast, other choices do not play a role in the function of ALA synthase. Vitamin C is primarily known for its antioxidant properties and role in collagen synthesis. Nicotinic acid (niacin) is crucial in energy metabolism, particularly as a precursor for NAD and NADP, but it does not act as a cofactor for ALA synthase.