The malic enzyme metabolic switch. Malic enzyme mediates the conversion of malate to pyruvate, which is accompanied by the production of NADPH. NADPH is a necessary cofactor for the biosynthesis of fatty acids along with acetyl-CoA, generated by the metabolism of ethanol. The diagram highlights auxiliary pathways for the biosynthesis of fatty acids. Pyruvate carboxylase and malic enzyme mediate a cyclic metabolic pathway, which via the mitochondrial citrate and pyruvate transporters results in the transport of acetyl-CoA across the mitochondrial membrane and generation of cytosolic NADPH. An alternative metabolic pathway is the direct conversion of pyruvate into acetyl-CoA via the pyruvate dehydrogenase complex. This metabolic switch channels excess metabolic energy into the synthesis of fatty acids and contributes to the development of fatty liver syndrome during excessive alcohol consumption. Modified from .