Pyruvate formate-lyase half-reactions

The details of the process and the oxidation-reduction balance can be pictured as in Eq. 17-25. Pyruvate is cleaved by the pyruvate formate-lyase reaction (Eq. 15-37) to acetyl-CoA and formic acid. Half of the acetyl-CoA is cleaved to acetate via acetyl-P with generation of ATP, while the other half is reduced in two steps to ethanol using the two molecules of NADH produced in the initial oxidation of triose phosphate (Eq. 17-25). The overall energy yield is three molecules of ATP per glucose. The "efficiency" is thus (3 x 34.5)... 

Pyruvate formate-lyase (EC 2.3.1.54 formate acetyltransferase PEL) catalyzes the key reaction in anaerobic glucose metabolism in bacteria, the coenzyme A-dependent dismutation of pyruvate into acetyl-CoA and formate. The reaction, first reported by Werkman and co-workers in the early 1940s (169, 170), was described as the phosphoroclastic cleavage of pyruvate because acetyl phosphate was detected as a product. Following the discovery of CoA and the elucidation of its role in acetyl transfer reactions (77/, 772), the intermediacy of acetyl-CoA in pyruvate dismutation was realized the overall reaction catalyzed by PFL is generally described by two half-reactions (Scheme 37). 

Scheme 37. Half-reactions of pyruvate formate-lyase 187).

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