Mechanism of Malate Utilization in Ascaris‐Muscle Mitochondria

1 The penetration of malate into Ascaris-muscle mitochondria and its metabolic conversion have been studied. 2 It is shown that Pi is required for the entry of malate into the mitochondria. In fact Pi activates: (1) the swelling of Ascaris-muscle mitochondria suspended in ammonium-malate; (2) the reduction by malate of mitochondrial nicotinamide nucleotides and flavoproteins; (3) the conversion of malate into other metabolites. Butylmalonate abolishes the activating effect of Pi on malate penetration into Ascaris-muscle mitochondria. 3 The activation by Pi of nicotinamide nucleotide reduction is followed at higher Pi concentrations by inhibition. 4,5,6,7-Tetrachloro-2-trifluoromethyl-benzimidazole inhibits the malatelinked reduction of nicotinamide nucleotides and flavoproteins. 4 Evidence is provided that in Ascaris-muscle two malate dehydrogenases are operative: the malic enzyme and the l-malate: NAD oxidoreductase.