6-Phosphogluconate dehydrogenase, pentose phosphate

Early work on the pathway started by this enzyme demonstrated that it led through phosphogluconate to pentose phosphate and typical products of triose phosphate degradation. However, it is only in recent years that this problem occasioned sufficient interest to provoke study of the precise nature of the intermediates of the pathway and enzyme distribution in various organisms. The presence of the glucose-6-phosphate dehydrogenase has been established in yeast, E. Pseudomonas strains, - ... 

Figure 18.10 The hexose monophosphate shunt pathway. A, glucose-6-phosphate dehydrogenase B, 6-phosphogluconate dehydrogenase C, pentose-5-phosphate iso-merase D, pentose phosphate epimerase E, transaldolase F, transketolase G, phospho-hexoseisomerase. (Reproduced by permission from Williams JF. A critical examination of the evidence for the reactions of the pentose pathway in animal tissues. Trends Biochem Sri December 316, 1980.)...

Figure 6.4. Role of transketolase in the pentose phosphate pathway. Glucose 6-phosphate dehydrogenase, EC 1.1.1.49 phosphogluconate dehydrogenase, EC 1.1.1.44 rihulose-phosphate epimerase, EC 5.1.3.1 phosphorihose isomerase, EC 5.3.1,6 transketolase, EC 2.2.1.1 and transaldolase, EC 2.2.I.2.

NADPH, which provides the reducing equivalents for fatty acid synthesis, is produced by the inducible malic enzyme and by the inducible enzymes of the pentose phosphate pathway, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. 

The NADPH is provided by the pentose phosphate pathway. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase are inhibited by NADPH at the concentrations found in the unstimulated phagocyte. As NADPH is consumed by NADPH oxidase, inhibition of the pentose phosphate pathway is reduced, increasing the rate of formation of NADPH. 

Fig. 8. Pathways involved in the conversion of glucose to fatty acid. Reaction (1) is catalyzed by cytosolic malate dehydrogenase. Reaction (2) is catalyzed by mitochondrial malate dehydrogenase. (T) designates tricarboxylate anion transporter. Reactions catalyzed by glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the pentose phosphate pathway produce NADPH. CS, citrate synthase ACL, ATP citrate lyase PDH, pyruvate dehydrogenase complex ACC, acetyl-CoA carboxylase FAS, fatty acid synthase.

Ribulose-5-phosphate is a pentose phosphate pathway intermediates produced by 6-phosphogluconate dehydrogenase catalyzed oxidation of 6-phosphogluconolactone. 

Phosphogluconate dehydrogenase is an enzyme of the pentose phosphate pathway that catalyzes the reaction below ... 

Phosphogluconate Dehydrogenase An enzyme of the oxidoreductase class that catalyzes the reaction 6-phospho-D-gluconate and NADP+ to yield D-ribulose 5-phosphate, carbon dioxide, and NADPH. The reaction is a step in the pentose phosphate pathway of glucose metabohsm. (From Borland, 27th ed) EC 1.1.1.43. [nih]... 

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