Alternate Fates of Pyruvate
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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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