Glycolysis glyceraldehyde*3*phosphate

Glycolysis Glyceraldehyde-3-phosphate dehydrogenase Phosphoglycerate kinase Pyruvate kinase... 

During glycolysis, glyceraldehyde 3-phosphate is converted to 1,3-bisphosphoglycerate and the equilibrium of the adenylate kinase reaction lies in favor of 3-phosphoglycerate, so the metabolites are drawn through the pathway of reactions. 

Glycolysis, glyceraldehyde-3-phosphate dehydrogenase and, 46-49 Glyoxylate, succinate dehydrogenase and, 238... 

In the second phase of glycolysis, glyceraldehyde-3-phosphate is converted to pyruvate. 

The idea that enzymes whose normal substrate is orthophosphate can use arsenate in its place, and that the esters of arsenate formed are rapidly hydrolyzed, was given by Braunstein (16) in 1931, to explain the effects of arsenate on glycolysis. This idea was formulated more precisely for glyceraldehyde-phosphate dehydrogenase in 1939. This enzyme, E—SH, normally oxidizes its aldehyde substrate with phosphate uptake to give an acyl phosphate, as follows ... 

Glyceraldehyde phosphate dehydrogenase Catalyzes important step in glycolysis... 

Fig. 8.22. Isomerases rearrange atoms within a molecule. In the pathway of glycolysis, triose phosphate isomerase converts dihydroxyacetone phosphate to glyceraldehydes 3-phos-phate by rearranging hydrogen atoms. No other substrates or products of the reaction exist.

Glycerophosphate dehydrogenase, from yeast, converts a-glycerophosphoric acid into glyceraldehyde phosphate, and subsequently into phosphoglyceric acid, all of which participate in glycolysis. Adenosine triphosphate is the co-enzyme of the... 

This cleavage is a retro aldol reaction It is the reverse of the process by which d fruc tose 1 6 diphosphate would be formed by aldol addition of the enolate of dihydroxy acetone phosphate to d glyceraldehyde 3 phosphate The enzyme aldolase catalyzes both the aldol addition of the two components and m glycolysis the retro aldol cleavage of D fructose 1 6 diphosphate... 

Further steps m glycolysis use the d glyceraldehyde 3 phosphate formed m the aldolase catalyzed cleavage reaction as a substrate Its coproduct dihydroxyacetone phosphate is not wasted however The enzyme triose phosphate isomerase converts dihydroxyacetone phosphate to d glyceraldehyde 3 phosphate which enters the glycol ysis pathway for further transformations... 

The triose phosphate isomerase reaction completes the first phase of glycolysis, each glucose that passes through being converted to two molecules of glyceraldehyde-3-phosphate. Although the last two steps of the pathway are... 

Dihydroxyacetone phosphate is of course an intermediate in glycolysis. D-Gly-ceraldehyde can be phosphorylated by triose kinase in the presence of ATP to form D-glyceraldehyde-3-phosphate, another glycolytic intermediate. 

How might iodoacetic acid affect the glyceraldehyde-3-phosphate dehydrogenase reaction in glycolysis Justify your answer. 

N/ JDPH is considerably greater than the need for ribose-5-phosphate. The next three steps thus return some of the five-carbon units to glyceraldehyde-3-phos-phate and fructose-6-phosphate, which can enter the glycolytic pathway. The advantage of this is that the cell has met its needs for N/VDPH and ribose-5-phosphate in a single pathway, yet at the same time it can return the excess carbon metabolites to glycolysis. 

The transaldolase functions primarily to make a useful glycolytic substrate from the sedoheptulose-7-phosphate produced by the first transketolase reaction. This reaction (Figure 23.35) is quite similar to the aldolase reaction of glycolysis, involving formation of a Schiff base intermediate between the sedohep-tulose-7-phosphate and an active-site lysine residue (Figure 23.36). Elimination of the erythrose-4-phosphate product leaves an enamine of dihydroxyacetone, which remains stable at the active site (without imine hydrolysis) until the other substrate comes into position. Attack of the enamine carbanion at the carbonyl carbon of glyceraldehyde-3-phosphate is followed by hydrolysis of the Schiff base (imine) to yield the product fructose-6-phosphate. 

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