Niacin adenine dinucleotide phosphate

These enzymes generate cyclic ADP-ribose and 2-phospho-cyclic ADP-ribose from NAD and NADP, respectively. Both molecules trigger cyclic ADP-ribose cytosolic Ca elevation, presumably by activating the ryanodine receptor in the endoplasmic/sarcoplasmic reticulum (Poliak et al. 2007). In addition to cyclic ADP-ribose, niacin adenine dinucleotide phosphate, a metabolite of NADP, can also mobilize stores. The release mechanism and the stores on which niacin adenine dinucleotide phosphate acts are from lysosomal Ca " stores, which are independent of the stores of activated by cyclic ADP-ribose or inositol 1,4,5-trisphosphate (Yamasaki et al. 2004). 

Niacin. Figure 2 Structure of the coenzymes NAD+ (nicotinamide-adenine dinucleotid) and NADP+ (nicotinamide-adenine dinucleotid phosphate). 

NADP can be converted to nicotinic acid adenine dinucleotide phosphate (NAADP), which has distinct functions in the regulation of intracellular calcium stores. The studies of these new roles of NAD(P) in metabolism are in their early stages, but they might soon help to better understand and explain the symptoms of niacin deficiency ( pellagra) [1]. 

These dehydrogenases use nicotinamide adenine dinucleotide (NAD ) or nicotinamide adenine dinucleotide phosphate (NADP )—or both—and are formed in the body from the vitamin niacin (Chapter 45). The coenzymes are reduced by the specific substrate of the dehydrogenase and reoxidized by a suitable electron acceptor (Figure 11-4). They may freely and reversibly dissociate from their respective apoenzymes. 

Although the structures for molecules having niacin activity are simple, the forms in which they act in human biochemistry are not so simple. Nicotinic acid and nicotinamide are precursors for three complex coenzymes in multiple oxida-tion/reduction (redox) reactions nicotinamide mononucleotide, NMN nicotinamide adenine dinucleotide, NAD+ and nicotinamide adenine dinucleotide phosphate, NADP. I shall use NAD+ as representative of the class. NADH is the corresponding reduced form. ... 

Nicotinate and nicotinamide, together referred to as niacin, are required for biosynthesis of the coenzymes nicotinamide adenine dinucleotide (NAD"") and nicotinamide adenine dinucleotide phosphate (NADP" ). These both serve in energy and nutrient metabolism as carriers of hydride ions (see pp. 32, 104). The animal organism is able to convert tryptophan into nicotinate, but only with a poor yield. Vitamin deficiency therefore only occurs when nicotinate, nicotinamide, and tryptophan are all simultaneously are lacking in the diet. It manifests in the form of skin damage (pellagra), digestive disturbances, and depression. 

Niacin is also known as vitamin PP or vitamin Bj. The term niacin describes two related compounds, nicotinic acid and nicotinamide (Figure 19.18), both with biological activity. Niacin is formed from the metabolism of tryptophan, and therefore it is not strictly a vitamin. It is a precursor of two cofactors nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are essential for the functioning of a wide range of enzymes involved in redox reactions. 

Niacin is a generic term which refers to two related chemical compounds, nicotinic acid (6.22) and its amide, nicotinamide (6.23) both are derivatives of pyridine. Nicotinic acid is synthesized chemically and can be easily converted to the amide in which form it is found in the body. Niacin is obtained from food or can be synthesized from tryptophan (60 mg of dietary tryptophan has the same metabolic effect as 1 mg niacin). Niacin forms part of two important co-enzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are co-factors for many enzymes that participate in various metabolic pathways and function in electron transport. 

Nicotinamide adenine dinucleotide (NAD+ in its oxidized form) and its close analog nicotinamide adenine dinucleotide phosphate (NADP+) are composed of two nucleotides joined through their phosphate groups by a phosphoanhydride bond (Fig. 13-15a). Because the nicotinamide ring resembles pyridine, these compounds are sometimes called pyridine nucleotides. The vitamin niacin is the source of the nicotinamide moiety in nicotinamide nucleotides. 

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... 

Niacin, a water-soluble vitamin vital for oxidation by living cells, functions in the body as a component of two important coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are involved in the release of energy from carbohydrate, fat, and protein, and in the synthesis of protein, fat, and pentoses for nucleic acid formation. Milk is a poor source of preformed niacin, containing about 0.08 mg per 100 g. However, milk s niacin value is considerably greater than indicated by its niacin content (Horwitt et al. 1981). Not only is the niacin in milk fully available, but the amino acid tryptophan in milk can be used by the body for the synthesis of niacin. For every 60 mg of tryptophan consumed, the body synthesizes 1 mg of niacin. Therefore, the niacin equivalents in 100 g milk equal 0.856 mg including that from pre-... 

Niacin production of reduced nicotinamide adenine dinucleotide (phosphate) (NADPH) by ACTH via cyclic adenosine monophosphate (AMP)... 

The niacin vitamers in foods include nicotinic acid and nicotinamide (Fig. 4), which occur in limited quantities in the free form, and their coenzymes, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) (93,96). The nicotinic acid analog of NAD as well as nicotinamide and nicotinic acid mononucleotides also occur in nature. In addition, niacin occurs as nicotinyl esters bound to polysaccharides, peptides, and glycopep-tides, which are known as niacytin and niacynogens, respectively. In general, the niacin vitamers in cereal grains and other seeds are principally the nicotinic acid forms, whereas those in meat and fish are primarily the nicotinamide forms (94,95). 

Niacin is unusual among the vitamins in that it was discovered as a chemical compound, nicotinic acid produced by the oxidation of nicotine, in 1867 -long before there was any suspicion that it might have a role in nutrition. Its metabolic function as part of what was then called coenzyme II [nicotinamide adenine dinucleotide phosphate (NADP)] was discovered in 1935, again before its nutritional significance was known. 

Niacin is required for the S5mthesis of the active forms of vitamin B3, nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+). 

Niacin and niacinamide (nicotinamide and nicotinic acid amide) are converted to the ubiquitous redox coenzymes nicotinamide-adenine dinucleotide (NAD)" and nicotinamide-adenine dinucleotide phosphate (NADP). ... 

Nicotinamide-adenine dinucleotide (NAD diphosphopyri-dine nucleotide) and nicotinamide-adenine dinucleotide phosphate (NADP also termed triphosphopyridine nucleotide) represent most of the niacin activity found in good sources that include yeast, lean meats, liver, and poultry. Milk, canned salmon, and several leafy green vegetables contribute lesser amounts but are still sufficient to prevent deficiency. Additionally, some plant foodstuffs, especially cereals such as corn and wheat, contain niacin bound to various peptides and sugars in forms nutritionally not readily available (niacinogens or niacytin). Because tryptophan is a precursor of niacin, protein provides a considerable portion of niacin equivalent. As much as two thirds of niacin required by adults can be derived from tryptophan metaboHsm via nicotinic acid ribonucleotide... 

Co-enzyme I (nicotinamide-adenine dinucleotide NAD) and Co-enzyme II (nicotinamide-adenine dinucleotide phosphate NADP) are required by all living cells. They enable both the conversion of carbohydrates into energy as well as the metabolism of proteins and fats. Both nicotinamide and nicotinic acid are building blocks for these co-enzymes. The common name for the vitamin is niacin and, strictly speaking, refers only to nicotinic acid. 

The answer is a. (Murray, pp 627-661. Scriver, pp 3897-3964. Sack, pp 121—138. Wilson, pp 287-320.) The major contributor of electrons in reductive biosynthetic reactions is nicotinamide adenine dinucleotide phosphate (NADPH -I- H ), which is derived by reduction of NAD. NAD is formed from the vitamin niacin (also called nicotinate). Niacin can be formed from tryptophan in humans. In the synthesis of NAD, niacin reacts with 5-phosphoribosyl-l-pyrophosphate to form nicotinate ribonucleotide. Then, AMP is transferred from ATP to nicotinate ribonucleotide. Finally, the amide group of glutamate is transferred to the niacin carboxyl group to form the final product, NAD. NADP is derived from NAD by phosphorylation of the 2 -hydroxyl group of the adenine ribose moiety. The reduction of NADP to NADPH -I- H occurs primarily through the hexose monophosphate shunt. 

Niacin (Vitamin B3) and Nicotinamide Adenine Dinucleotide Phosphate (NADP )... 

Niacin (B3) Nicotinamide adenine dinucleotide (NAD" ) Nicotinamide adenine dinucleotide phosphate (NADP" ) Carrier of hydride ions... 

Nicotinamide adenine dinucleotide (NAD) is the coenzyme form of the vitamin niacin. Most biochemical reactions require protein catalysts (enzymes). Some enzymes, lysozyme or trypsin, for example, catalyze reactions by themselves, but many require helper substances such as coenzymes, metal ions, and ribonucleic acid (RNA). Niacin is a component of two coenzymes NAD, and nicotinamide adenine dinucleotide phosphate (N/kDP). NAD (the oxidized form of the NAD coenzyme) is important in catabolism and in the production of metabolic energy. NADP (the oxidized form of NADP) is important in the biosynthesis of fats and sugars. 

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