Hexose diphosphate dehydrogenase

Hexose diphosphate dehydrogenase, from muscle, liver, cucumber seed and other sources, activates fructose diphosphate. 

The natural substrate for the dehydrogenase, glyceraldehyde-3-phosphate (G-3-P), had been synthesized earlier by Hermann Fischer, Emil Fischer s son, and Baer in 1932. In 1934 Meyerhof and Lohmann synthesized hexose diphosphate, establishing it to be fructose 1,6 bisphosphate (F-l, 6 bis P). With F-1,6 bisP as substrate and hydrazine to trap the aldehydic and ketonic products of the reaction, G-3-P was identified in the mixture of G-3-P and dihydroxyacetone phosphate which resulted. Triose phosphate isomerase was then isolated and the importance of phosphorylated 3C derivatives established. 

Whether coenzyme I was concerned in the earlier experiments was not determined and has not mnce been determined. The evidence from these studies was suggestive of the participation of ascorbic acid as a respiratory carrier. It was, however, only suggestive and not conclusive, for the authors did not demonstrate either with their lactate dehydrogenase or hexose diphosphate systems the direct reduction of dehydroascorbic acid to ascorbic acid. 

A second phase in the study of the fermentative systems of bacteria was the preparation of cell-free extracts capable of fermenting glucose. Thus, it was demonstrated in 1940 that a cell-free juice could be prepared from E. coli which contained triosephosphate dehydrogenase and aldolase and which, in the presence of arsenate, DPN, and fluoride, could degrade hexose diphosphate to phosphoglyceric acid. ... 

Go-dehydrogenase I, co-enzyme I or co-zymase, obtainable from extracts of yeast, muscle, liver and kidney, is the co-enzyme of sugar fermentation, and acts with the dehydrogenases of hexose diphosphate, malate, and alcohol, and also with the lactate dehydrogenase of muscle. 

The basis of the action of iodoacetate on muscle contraction was uncovered by Dickens and Rapkine (ca. 1933). They found iodoacetate alkylated SH groups on proteins, especially those in glyceraldehyde 3-phosphate dehydrogenase (G-3-PDH). When the enzyme was inhibited precursors accumulated—hexose mono- and diphosphates—as in Lundsgaard s experiments. 

---