Glyceraldehyde conditions

Calculate the value of A l,/ for the glyceraldehyde-3-phos-phate dehydrogenase reaction, and calculate the free energy change for the reaction under standard-state conditions. 

BOTH NADPH AND ATP ARE NEEDED BY THE CELL, BUT RmOSE-5-P IS NOT Under some conditions, both NADPH and ATP must be provided in the cell. This can be accomplished in a series of reactions similar to case 3, if the fructose-6-P and glyceraldehyde-3-P produced in this way proceed through glycolysis to produce ATP and pyruvate, which itself can yield even more ATP by continuing on to the TCA cycle (Figure 23.40). The net reaction for this alternative is... 

This reaction is followed by another phosphorylation with ATP catalyzed by the enzyme phosphofructoki-nase (phosphofructokinase-1), forming fructose 1,6-bisphosphate. The phosphofructokinase reaction may be considered to be functionally irreversible under physiologic conditions it is both inducible and subject to allosteric regulation and has a major role in regulating the rate of glycolysis. Fructose 1,6-bisphosphate is cleaved by aldolase (fructose 1,6-bisphosphate aldolase) into two triose phosphates, glyceraldehyde 3-phosphate and dihydroxyacetone phosphate. Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate are inter-converted by the enzyme phosphotriose isomerase. 

Metal hahdes in imidazolium ionic hquids offer unique enviromnents able to facihtate dehydration reactions. Under such conditions certain metal halides are able to catalyze formal hydride transfer reactions that otherwise do not occur in the ionic liquid media. We have now discovered two systems in which this transformation has been observed. The initial system involves the conversion of glucose to fractose followed by dehydration the second system involves the dehydration of glycedraldehyde dimer followed by isomerization to lactide. CrCls" anion is the only catalyst that has been effective for both systems. VCI3" is effective for the glyceraldehyde dimer system but not for glucose. 

Glyceraldehyde phosphate and dihydroxyacetone phosphate react in the presence of aldolase to yield fructose diphosphate as the only product under physiolocial conditions. 

The reaction protocol was further extended to the concise synthesis of poly-oxamic acid, the unique polyhydroxyamino acid side-chain moiety of the antifungal polyoxin antibiotics (63). Treatment of the template 205 under standard thermal cycloaddition conditions with (5)-glyceraldehyde acetonide led to the formation of a single diastereoisomer 208 in 53% yield. Subsequent template removal released polyoxamic acid 209 in essentially quantitative yield. This represents a matched system, with the mismatched system leading to more complex reaction mixtures (Scheme 3.70). 

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