Biochemistry

Nicotinic acid (niacin, nicotinamide, vitamin PP, antipellagric factor). Nicotinic acid has been known since 1867. It was synthesized in 1873. In 1937-1939 nicotinic acid has been proven to be an anti-pellagric vitamin. Structure and physicochemical properties. Biologically active substances are nicotinic acid and its amide - nicotinamide. It is the main component in a number of enzymes. Nicotinic acid is a pyridine compound containing a carboxyl group (nicotinamide differs, respectively, by the presence of an amine group). • H • H ■ | 1 н ү с ү< . H-C\ ^C-H N yvc H-C\ ^C-H N Nicotinic acid Nicotinamide HC^ 4 C — of + (2Н + ,2ё) I I! x nh 2 h <W h N I R Nicotinamide (oxidized form) H H X HC C — + H + II II 4 nh 2 hc 4 Z CH N (in solution) R Nicotinamide (reduced form) Nicotinic acid is a white crystalline substance, slightly acidic in taste, highly soluble in water and ethanol. It is stored in foods, resistant to chemical and physical agents. It withstands drying, prolonged heating at high temperature. During cooking 15-20% is destroyed. Biological role. The vitamin PP value is associated with its participation in the composition of anaerobic dehydrogenases in redox reactions. Many pyridine-dependent enzymes are known that transfer electrons and protons from oxidizable substrates to flavoproteins. Dehydrogenases associated with NAD are involved mainly in the process of electron transfer from the substrate through FAD to oxygen. In the process of dehydrogenation, the substrate is released from two hydrogen atoms (2H or 2H + + 254