Nicotinamide vitamin

Two vitamins, nicotinamide and pyridoxine (vitamin B6), are pyridine derivatives. Nicotinamide participates in two coenzymes, coenzyme I (65 R = H) which is known variously as nicotinamide adenine dinucleotide (NAD) or diphosphopyridine nucleotide (DPN), and coenzyme II (65 R = P03H2) also called triphosphopyridine nucleotide (TPN) or nicotinamide adenine dinucleotide phosphate (NADP). These are involved in many oxidation-reduction processes, the quaternized pyridine system acting as a hydrogen acceptor and hydrogen donor. Deficiency of nicotinamide causes pellagra, a disease associated with an inadequately supplemented maize diet. Nicotinic acid (niacin) and its amide are... 

Two derivatives of nicotinamide (pyridine-3-carboxylic amide), one of the B2 vitamins, nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ), serve as redox coenzymes. Of the three heterocyclic ring systems found in these coenzymes, i.e. those of purine, ribose and pyridine, it is the pyridine portion that is reactive in redox reactions. Biologically, two oxidation states are important the oxidized form, NAD(P)+, and the 1,4-dihydro isomer of the two-electron reduced form, NAD(P)H (Scheme 1). Nicotinamide coenzymes interconvert between these two oxidation states in... 

These physiologically active natural compounds 307 and 308 have been labelled with in a simple and rapid one-step ammonolysis reaction (equations 124 and 125) in sealed glass vials. They were used for studies of biological function and in nuclear-medical studies. [ N]nicotinamide (NAM) has been found to be a useful tracer for studying the utilization of the vitamin, nicotinamide . A comparison of the distribution of [ N]NAM with that of [ C]NAM has been carried out . ... 

The first of these coenzymes, nicotinamide adenine dinucleotide (NAD ), is a derivative of ADP and the vitamin nicotinamide (see > Figure 12.18). The reactive site of NAD is located in the nicotinamide portion of the molecule. During the oxidation of a substrate, the nicotinamide ring of NAD accepts two electrons and one proton, which forms the reduced coenzyme NADH. 

NAD is the active form of a vitamin, nicotinamide. The evidence available indicates that nicotinic acid is the intermediate in NAD synthesis. Thus, if the vitamin nicotinamide is used for NAD synthesis, it is used only after deamination. Nicotinic acid reacts with PRPP to yield the mononucleotide of nicotinic acid which forms deamido NAD in the presence of ATP and an enzyme present in liver nuclei. The amida-tion of the deamido NAD occurs in the presence of ATP, glutamine, and an enzyme present in the supernatant of liver homogenates. 

Coenzyme I might be considered as a mixed dinucleotide consisting of adenylic acid and a second nucleotide compound which has one of the B-complex vitamins (nicotinamide) as the nitrogen base. Almond emulsin hydrolyzes coenzyme I and iV -ribosylnicotinamide may be separated from the hydrolyzate 138),... 

Isotopically labeled vitamins nicotinamide-( 1 4] thiamine chloride-[ Cs] calcium pantothenate moncrfiydrate-f Cj, pyridoxine hydrochloride-... 

An inborn error in which there is defective intestinal and renal transport of neutral amino acids, one of these being tryptophan. This amino acid is normally converted to the vitamin, nicotinamide. The clinical features of Hartnup disease are similar to the nicotinamide deficiency disease, pellagra, being due to the low amounts of tryptophan available for nicotinamide synthesis. The disease can be diagnosed by the presence of large amounts of indole compounds in the urine, which result from the action of gut bacteria on the unabsorbed dietary tryptophan. 

It can be converted by intestinal flora and probably by the tissues to the vitamin, nicotinamide. A dietary deficiency of tryptophan can therefore result in nicotinamide deficiency if dietary intake of nicotinamide is also low. Symptoms resembling those of nicotinamide deficiency can also occur in the inborn error, Hartnup disease, where body tryptophan levels are reduced due to diminished reabsorption of the amino acid from the renal tubules. 

Metabolism of Tryptophan. The catabolism of tryptophan is interesting since it leads to the biosynthesis of a vitamin, nicotinamide. It appears contradictory to state that a vitamin is formed by an organism, but nicotinamide deficiency can indeed be demonstrated only with the concurrent deficiency of vitamin Be. Tryptophan largely replaces the vitamin even in man. 

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