I27. the Oxidation of Pyruvate by Heart Muscle

BRAuN-MENENDEZ et al. [1939], working with heart-lung and isolated heart preparations, have shown that pyruvate can be utilized by the mammalian heart. Minced heart muscle, as will be seen later, oxidizes pyruvate at about the same rate as the intact heart, and it was used in the present work for a study of the mechanism of the oxidation of pyruvate. The object of the investigation was to determine whether oxidation occurs by way of the citric acid cycle as in pigeon breast muscle [Krebs & Eggleston, 1940]. The main evidence for the occurrence of the citric acid cycle in pigeon breast muscle is as follows: (1) The oxidation of pyruvate is inhibited by malonate. (2) The malonate inhibition is partially overcome by the addition offumarate, and the extra amount of pyruvate used in these conditions is in the proportion of 1 mol. of pyruvate to each mol. of added fumarate. In the presence of malonate succinate is formed in amounts equivalent to the fumarate added, the reaction being fumarate +pyruvate + 202 succinate + 3CO2+ H20. (1)