Figure 1.

NADH-fumarate reductase system in A. suum adult mitochondria and inhibition site of nafuredin. In the phosphoenolpyruvate carboxykinase (PEPCK)-succinate pathway, phosphoenolpyruvate (PEP) produced by a glycolytic process is carboxylated to form oxaloacetate and is then reduced to malate. The cytosolic malate is transported into the mitochondria, where it is first reduced to fumarate, and finally to succinate by the rhodoquinol-fumarate reductase activity of complex II. The terminal step is catalyzed by the NADH-fumarate reductase system comprising complex I, rhodoquinone (RQ), and complex II, as described in the text. Aerobic and anaerobic respiratory chains are boxed in broken lines. Electron-transfer flavoprotein (ETF) dehydrogenase:rhodoquinone branch () is also included. ETF-DH, ETF-dehydrogenase; ECR, enoyl-CoA reductase.