The oxidation of pyruvate by isolated heart sarcosomes

• 1.1. Although heart sarcosomes are able rapidly to oxidize glutamate to aspartate for periods exceeding 1 h at 25°, the oxidation of pyruvate declines rapidly after about 1 min.
• 2.2. Pyruvate inhibits the oxidation of glutamate, whether added before or after the glutamate.
• 3.3. Acetoacetate inhibits the oxidation of both glutamate and pyruvate. The respiration is completely restored by the addition of catalytic amounts of malate or of α-oxoglutarate.
• 4.4. It is concluded that the inhibitions are caused by decarboxylation of oxaloacetate, catalysed by acetyl-CoA, produced by oxidation of pyruvate or from the acetoacetyl-CoA formed by reaction of acetoacetate with succinyl-CoA.