Biosynthesis

The liver can synthesize niacin from the essential amino acid tryptophan, but the synthesis is extremely inefficient, 60 mg of tryptophan are required to synthesize 1 mg of niacin. The 5 member heterocyclic aromatic essential amino acid tryptophan, are rearmed with alpha amino group of tryptophan in the 6-membered heterocyclic aromatic niacin. Josyann Abisaab Different forms of niacin are contained in food (animal and plant), being as niacinamide, nicotinic acid, which are absorbed in the small intestine, then enter the circulation and from them is synthesized NAD and NADP, active forms of the vitamin. These are stored as NAD and NADP mainly in liver and erythrocytes.The 5 member heterocyclic aromatic essential amino acid, tryptophan, are rearmed with alpha amino group of tryptophan in the 6-membered heterocyclic aromatic niacin for the following reaction: Biosynthesis: Tryptophan kynurenine niacin