VII. ALTERNATE FATES OF PYRUVATE A. Oxidative decarboxylation of pyruvate Oxidative decarboxylation of pyruvate by pyruvate dehydrogenase complex is an important pathway in tissues with a high oxidative capacity, such as cardiac muscle (Figure 8.24). Pyruvate dehydro- genase irreversibly converts pyruvate, the end product of glycolysis, into acetyl CoA, a major fuel for the TCA cycle (see p. 109) and the building block for fatty acid synthesis (see p. 183). B. Carboxylation of pyruvate to oxaloacetate Carboxylation of pyruvate to oxaloacetate (OAA) by pyruvate carboxylase is a biotin-dependent reaction (see Figure 8.24). This reaction is important because it replenishes the citric acid cycle inter- mediates, and provides substrate for gluconeogenesis (see p. 118). 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 micro - organisms, but not in humans. The enzyme requires thiamine pyro - phosphate as a coenzyme, and catalyzes a reaction similar to that described for pyruvate dehydrogenase (see p. 110).