Glyceraldehyde reduction

FIGURE 19.30 (a) Pyruvate reduction to ethanol in yeast provides a means for regenerating NAD consumed in the glyceraldehyde-3-P dehydrogenase reaction, (b) In oxygen-depleted muscle, NAD is regenerated in the lactate dehydrogenase reaction. 

They accomplish the reduction of 3-phosphoglycerate, the primary product of COg fixation, to glyceraldehyde-3-phosphate so that carbohydrate synthesis becomes feasible. 

Reduction of the acyl phosphate gives glyceraldehyde 3-phosphate, which Q undergoes keto-enol tautomerization to yield dihydroxyacetone phosphate. 

Problem 29.13 Write a mechanism for step 6 of gluconeogenesis, the reduction of 3-phospho-glyceryl phosphate with NADH/H+ to yield glyceraldehyde 3-phosphate. 

A somewhat similar configurational correlation between (leva)-glyceraldehyde and (dexfro)-lactic acid has been made by Wolfrom, Lemieux, Olin and Weisblat.36 Reductive desulfurization of tetra-acetyl-2-methyl-D-glucose diethyl thioacetal (XXVII) and hydrolysis of the product gave 2-methyl-l-desoxy-D-glucitol (XXVIII) oxidation... 

Reaction of D-glucono-1,4-lactone with 2,2-dimethoxypropane-tin(II) chloride yields the 5,6-0-isopropylidene derivative 13, which on periodate oxidation afforded 2,3-0-isopropylidene-D-glyceraldehyde (21). However, the acid-catalyzed isopropylidenation of D-glucono-1,5-lactone with 2,2-dimethoxypropane afforded methyl 3,4 5,6-di-0-isopropylidene-D-gluco-nate (14) as the main product (22). Reduction of the ester function gave... 

It remains undecided whether the formation of small amounts of glycerol reported by Oppenheimer in the case of zymase extract is due to a ph3rtochemical reduction of trioses. If hexoses are fermented in the presence of trioses with ordinary fresh yeasts which do not attack dihy-droxyacetone and glyceraldehyde, the added trioses are recovered practically unaltered after the disappearance of the hexoses. 

L-Mannitol has been prepared by the reduction of L-mannosaccharo-dilactone or L-mannose. By far the most convenient procedure is that used by Baer and Fischer for their preparation of L-glyceraldehyde by the oxidative cleavage of l,2 5,6-diisopropylidene-L-mannitol with lead tetraacetate. L-Arabinose was converted to L-mannonolactone by the cyanohydrin synthesis and this was hydrogenated over platinum oxide to the desired L-mannitol. High hydrogen pressures, rather than low as usually employed with this catalyst, were used. 

The reaction of alkyl dihalogenoacetate magnesium enolates with 2,3-isopropylidene-D-glyceraldehyde affords the expected /3-hydroxy-a-dihalogenoesters . The erythro isomer is obtained with isopropyl dichloroacetate magnesium enolate. This result is in agreement with theoretical models. 2-Deoxy-pentono-1,4-lactones are obtained after removal of the halogen atom by either Raney nickel or tributyltin hydride reduction (equation 89). 

The acceptor of hydrogen in the glyceraldehyde 3-phosphate dehydrogenase reaction is NAD+ (see Fig. 13-15), bound to a Rossmann fold as shown in Figure 13-16. The reduction of NAD+ proceeds by the enzymatic transfer of a hydride ion ( H ) from the aldehyde group of glyceraldehyde 3-phosphate to the nicoti-... 

FIGURE 20-4 The three stages of C02 assimilation in photosynthetic organisms. Stoichiometries of three key intermediates (numbers in parentheses) reveal the fate of carbon atoms entering and leaving the cycle. As shown here, three C02 are fixed for the net synthesis of one molecule of glyceraldehyde 3-phosphate. This cycle is the photosynthetic carbon reduction cycle, or the Calvin cycle. 

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