Glyceral-3-phosphate dehydrogenase

FIGURE 19.18 A mechanism for the glycer-aldehyde-3-phosphate dehydrogenase reaction. Reaction of an enzyme snlfliydryl with the carbonyl carbon of glyceraldehyde-3-P forms a thiohemiacetal, which loses a hydride to NAD to become a thloester. Phosphorolysls of this thloester releases 1,3-blsphosphoglycerate. 

Figure 17-3. Mechanism of oxidation of giyceraldehyde 3-phosphate. (Enz, glycer-aldehyde-3-phosphate dehydrogenase.) The enzyme is inhibited by the— 5H poison iodoacetate, which is thus abie to inhibit glycolysis. The NADH produced on the enzyme is not as firmly bound to the enzyme as is NAD. Consequently, NADH is easily displaced by another molecule of NAD". ...

Glyceraldehyde-3-phosphate dehydrogenase (NADP+) (nonphosphorylating) [EC 1.2.1.9], also referred to as triose-phosphate dehydrogenase, catalyzes the reaction of D-glyceraldehyde 3-phosphate with NADP+ and water to produce 3-phospho-D-glycerate and NADPH. 

Tatton W, Chalmers-Redman R, Tatton N. Neuroprotection by deprenyl and other propargylamines glycer-aldehyde-3-phosphate dehydrogenase rather than monoamine oxidase B. J Neural Transm. 2003 110 509-515. 

Step 6 involves the oxidation of D-glyceraldehyde 3-phosphate, accompanied by phosphorylation of the intermediate carboxylic acid, to produce D-l,3-bisphosphoglycerate. The enzyme is glyceral-dehyde-3-phosphate dehydrogenase. 

Furylacrylolyl phosphate, glyceral-dehyde-3-phosphate dehydrogenase and, 36, 36... 

Dastoor Z, Dreyer JL (2001) Potential role of nuclear tr anslocation of glycer aldehyde-3-phosphate dehydrogenase in apoptosis and oxidative str ess. J Cell Sci 114 Pt 9 1643—1653. 

Nicotinamide adenine dinudeotide (NADH)-cytochrome b5 reductase (EC 1.6.2.2 cytbSr) uses NADH generated in the reaction in the Embden-Meyerhof pathway by glycer-aldehyde 3-phosphate dehydrogenase, to reduce the 12kDa protein cytochrome b5. Cytochrome b5 in turn reduces methemoglobm to hemoglobin. 

Rainer TH, Lam NYL, Tsui NBY, Ng EKO, Chiu RWK, Joynt GM, et al. Effects of filtration on glycer-aldehyde-3-phosphate dehydrogenase mRNA in the plasma of trauma patients and healthy individuals. Clin Chem 2004 50 206-8. 

Tables 13-la and 13-lb list only the most important categories of enzyme classes (E.C. s). Some enzymes that are involved in reactions at phosphorus are hidden in other classes. For example glyceraldehyde-3-phosphate dehydrogenase, which catalyses the oxidative phosphorylation of glyceraldehyde-3-phosphate to 1,3-diphospho-glycerate, is classified under E.C. 1.2.1.12 and 1.2.1.13. Neither the name of the enzyme nor its IUB-classification, gives information about the phosphorylating step. Identifying enzymes potentially useful in synthesis that have been ambiguously classified is difficult for those outside of biochemistry because no complete reference is available connecting enzymatic activity with synthetic applicability.

For glyceraldehyde-3-phosphate dehydrogenase, conflicting conclusions have been reached by different workers (47 49). From one analysis of initial rate data, for the pig muscle enzyme, it appears that with glycer-aldehyde as substrate the mechanism is random (SO), whereas with glyceraldehyde 3-phosphate there is random combination of this substrate and NAD followed by phosphate as the compulsory third substrate (48). On the other hand, inhibition studies with the rabbit muscle enzyme indicate an ordered mechanism in which NAD is the first and acyl acceptor the last substrate to combine (51). More detailed comparative initial rate studies with the several aldehydes w hich act as substrates (Section II,E), preferably by a fluorimetric method (11,47), and isotope exchange studies at equilibrium are needed for this enzyme. 

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