Alternate Fates of Pyruvate

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Chapter: Biochemistry : Introduction to Metabolism and Glycolysis

Oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex is an important pathway in tissues with a high oxidative capacity such as cardiac muscle.


ALTERNATE FATES OF PYRUVATE



Figure 8.24 Summary of the metabolic fates of pyruvate. TPP = thiamine pyrophosphate. TCA = tricarboxylic acid; NAD(H) = nicotinamide adenine dinucleotide; CoA = coenzyme A.


A. Oxidative decarboxylation of pyruvate

Oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex is an important pathway in tissues with a high oxidative capacity such as cardiac muscle (Figure 8.24). Pyruvate dehydrogenase irreversibly converts pyruvate, the end product of glycolysis, into acetyl CoA, a major fuel for the TCA cycle and the building block for fatty acid synthesis.

 

B. Carboxylation of pyruvate to oxaloacetate

Carboxylation of pyruvate to oxaloacetate by pyruvate carboxylase is a biotin-dependent reaction (see Figure 8.24). This reaction is important because it replenishes the TCA cycle intermediates and provides substrate for gluconeogenesis.

 

C. Reduction of pyruvate to ethanol (microorganisms)

The conversion of pyruvate to ethanol occurs by the two reactions summarized in Figure 8.24. The decarboxylation of pyruvate by pyruvate decarboxylase occurs in yeast and certain other microorganisms but not in humans. The enzyme requires thiamine pyrophosphate as a coenzyme and catalyzes a reaction similar to that described for pyruvate dehydrogenase.

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