Glyceraldehyde-3-phosphate dehydrogenase function

Analyses of enzyme reaction rates continued to support the formulations of Henri and Michaelis-Menten and the idea of an enzyme-substrate complex, although the kinetics would still be consistent with adsorption catalysis. Direct evidence for the participation of the enzyme in the catalyzed reaction came from a number of approaches. From the 1930s analysis of the mode of inhibition of thiol enzymes—especially glyceraldehyde-phosphate dehydrogenase—by iodoacetate and heavy metals established that cysteinyl groups within the enzyme were essential for its catalytic function. The mechanism by which the SH group participated in the reaction was finally shown when sufficient quantities of purified G-3-PDH became available (Chapter 4). 

Zinc is essential for the functioning of at least twenty different enzymes, and their functions are widely varied. They include the alcohol dehydrogenases of yeast and mammalian liver, glyceraldehyde phosphate dehydrogenase, phosphoglycomutase of yeast, DNA and RNA polymerases (at least in bacteria), alkaline phosphatase in bacteria, mammalian carbo-xypeptidase, carbonic anhydrase, AMP hydrolase, pyruvate carboxylase (yeast), and aldolase (yeast and bacteria). The alkaline phosphatase of E, coli has, in each molecule, four atoms of zinc the two which maintain structure can be replaced by Mn, Co +, or Cu, whereas the other two atoms are essential for enzyme action (Trotman and Greenwood, 1971). 

It can function anaerobically by regenerating oxidized NAD (required in the glyceraldehyde-3-phosphate dehydrogenase reaction) by reducing pymvate to lactate. 

The essential—SH group in D-glyceraldehyde-3-phosphate dehydrogenase and the imidazol residues of the ribonuclease are also more reactive because of side-chain interactions in the active center. Such functional groups may have such extremely high reactivity that an equivalent amount of the reagent causes full inactivation of the enzyme. 

In enzymes, the most common nucleophilic groups that are functional in catalysis are the serine hydroxyl—which occurs in the serine proteases, cholinesterases, esterases, lipases, and alkaline phosphatases—and the cysteine thiol—which occurs in the thiol proteases (papain, ficin, and bromelain), in glyceraldehyde 3-phosphate dehydrogenase, etc. The imidazole of histidine usually functions as an acid-base catalyst and enhances the nucleophilicity of hydroxyl and thiol groups, but it sometimes acts as a nucleophile with the phos-phoryl group in phosphate transfer (Table 2.5). 

Fig. 35. Diagrammatic representation of functionally equivalent groups around the substrate in lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase and horse liver alcohol dehydrogenase. From the work of Rossmann and colleagues [164],...

It is not the purpose of this review to provide a comprehensive account of these structure-function studies however, the case of citrate synthase will be described briefly to illustrate the potential of such investigations. The studies on malate dehydrogenase are reviewed by Eisenberg et al. [81], and those on glyceraldehyde 3-phosphate dehydrogenase are described in detail in Chapter 7. 

Cell extracts of Pyrococcus contain low activities of fructose-1,6-bisphosphate aldolase [295] and NAD(P)-dependent glyceraldehyde-3-phosphate dehydrogenase [301, 308a], which probably have anabolic functions (see ref [308b]). Glyceraldehyde-3-phosphate dehydrogenase has been purified from Pyrococcus woesei [308a] (see Chapter 7 by Hensel in this volume). 

Ercolani, L., Florence, B., Denaro, M., Alexander, M. (1988). Isolation and complete sequence of a functional human glyceraldehyde-3-phosphate dehydrogenase gene. J. Biol. Chem. 263, 15335-15341. 

The X-ray crystallographic structures of lobster glyceraldehyde-3-phosphate dehydrogenase (G3PDH) (79) and dog fish lactate dehydrogenase (LDH) (20) show that the stereospecificity of hydride transfer is a function of the rotational... 

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