D-Glyceraldehyde-3-phosphate:NAD

The International Union of Biochemistry and Molecular Biology (IUBMB) developed a system of nomenclature in which enzymes are divided into six major classes (Figure 5.1), each with numerous subgroups. The suffix -ase is attached to a fairly complete description of the chemical reaction catalyzed, for example D-glyceraldehyde 3-phosphate NAD oxidoreductase. The IUBMB names are unambiguous and informative, but are sometimes too cumbersome to be of general use. 

D-glyceraldehyde 3-phosphate + phosphate + NAD(+) = 3-phospho-D-glyceroyl phosphate + NADH. 

BiosytMesis In animals tryptophan - kynutenine - 3-hydroxyanthranilic acid - quinolinic acid (pyri-dine-2,3-dicaiboxylic acid) - nicotinic acid - nicotinamide. In bacteria and higher plants from L- aspar-tic acid and a C3-unit, probably D-glyceraldehyde 3-phosphate. Also by cleavage of NAD. 

Figure 2. Redox cofactor requirement in L-arjabinose catabolism. L-Arabinose conversion to equimolar amounts of CO2 and ethanol is redox neutral, i- -anaerobic fermentation to ethanol should be possible. However, the conversion of L-arabinose to D-xylulose requires NADPH and NAD and produces NADH and NADP. NADPH is mainly regenerated in the oxidative part of the pentose phosphate pathway, where the reduction ofNADP is coupled to C02 production. The abbreviations are G6p, glucose 6-phosphate F6P, fructose 6-phosphate X5P, D-Xylulose 5-phosphate GAP, D-glyceraldehyde 3-phosphate. (Reproduced from Ref. 165 with permission from Elsevier Science)...

The D-glyceraldehyde-3-phosphate is converted into 1,3-diphosphoglyceric acid using inorganic phosphate, and electrons are transferred to the coenzyme NAD" -. The enzyme complex involved is called phosphoglyceraldehyde dehydrogenase. The reaction is the first in the EMP pathway to involve... 

To simplify structural formulas in Reaction 6, D-glyceraldehyde 3-phosphate is abbreviated G—CHO. Two changes occur in this reaction. First, the aldehyde group is oxidized to a carboxyl group, which is, in turn, converted to a mixed anhydride, and second, the oxidizing agent is NAD, which is reduced to NADH ... 

In most bacteria and in higher plants nicotinic acid is formed from aspartic acid and a three carbon unit derived from glycerol, probably D-glyceraldehyde-3-phosphate (D 2). A key intermediate is quinolinic acid, which in animals, however, is derived from l-tryptophan (D 21). Nicotinic acid originates from quinolinic acid via nicotinic acid mononucleotide formed with the participation of 5-phosphoribosyl-l-pyrophosphate. It changes either directly to nicotinic acid or is formed via nicotinamide adenine dinucleotide (NAD+) in the nicotinic acid nucleotide cycle. 

Lactate dehydrogenase-NAD-complex (dogfish) D-glyceraldehyde-3-phosphate dehydrogenase (lobster) (green) D-glyceraldehyde-3-phosphate dehydrogenase (lobster) (red)... 

Ostrem, J.A., Vernon, D.M. Bohnert, H.J. (1990). Stress increases the expression of a gene coding for NAD-glyceraldehyde 3-phosphate dehydrogenase during the transition from C3 photosynthesis to cras-sulacean acid metabolism in M. crystallinum. Journal of Biological Chemistry 265, 3497-502. 

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