2-oxoglutarate glucose oxidation

ThDP plays a crucial role as coenzyme for several enzymes and enzyme complexes such as transketolase (EC 2.2.1.1) and the enzyme complexes pyruvate (EC 1.2.4.1) and 2-oxoglutarate (EC 1.2.4.2) dehydrogenases, present in nearly all organisms. They play important catabolic roles and are key actors in cell energy metabolism (Figure 5.1). Reduced activity of these enzymes as a consequence of thiamin deficiency results in decreased glucose oxidation. As the brain heavily relies on oxidative metabolism, it is more severely affected by thiamin deficiency than other organs. 

Thiamine was the first vitamin to have its precise biochemical functions determined. In the form of its pyrophosphate, thiamine participates in several very important enzyme systems namely (1) pyruvate dehydrogenase (page 232) which converts pyruvate to acetyl-CoA and carbon dioxide in the course of carbohydrate breakdown (2) the reaction of the citrate cycle in which oxoglutarate is oxidatively decarboxylated to succinyl-CoA (page 242) (3) the transketolase reaction of the pentose phosphate pathway of glucose breakdown (page 233). 

The reaction, under the same conditions, has been extended to other /3-keto esters. Ethyl 3-oxovalerate, ethyl 3-oxohexanoate, and diethyl 3-oxoglutarate react with 2-amino-2-deoxy-D-glucose to give compounds (11), (12), and (13), respectively, whose oxidations with lead tetraacetate or periodic acid furnish the corresponding aldehydes (14), (IS), and (16). 

Bakg + Bqaa- Abbreviations T, activity of the citric acid dele P, activity of the oxidative pentose phosphate pathway Glc6P, glucose 6-phosphate Fru6P, fructose-6-phosphate Gra3P, glyceraldehyde 3-phosphate PEP, phosphoenolpyruvate PYR, pyruvate AcCoA, acetyl coenzymeA OAA, oxaloacetate, AKG, 2-oxoglutarate... 

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