Vitamin amino acids. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, vitamin E consists of four tocopherols and four tocotrienols. The thirteen vitamins required by human metabolism are: vitamin A (retinols and carotenoids), vitamin B (thiamine), vitamin B (riboflavin), vitamin B (niacin), vitamin B (pantothenic acid), vitamin B (pyridoxine), vitamin B (biotin), vitamin B (folic acid or folate), vitamin B (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones). Vitamins have diverse biochemical functions. Some forms of vitamin A function as regulators of cell and tissue
Vitamin B12-transporting ATPase Vitamin B12-transporting ATPase In enzymology, a vitamin B-transporting ATPase () is an enzyme that catalyzes the chemical reaction The 3 substrates of this enzyme are ATP, HO, and vitamin B, whereas its 3 products are ADP, phosphate, and vitamin B. This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides to catalyse transmembrane movement of substances. The systematic name of this enzyme class is ATP phosphohydrolase (vitamin B-importing). This enzyme participates in abc transporters - general. As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .