The fate of oxaloacetic acid in different organs

Abstract

SZENT-GY6RGYI and collaborators [1935] have shown that oxaloacetic acid (in this paper referred to as OAA) plays an essential part in the system of 04dicarboxylic acids concerned with the transport of H from the donators to 02. OAA, by accepting H, is reversibly hydrogenated to l-malic acid (very likely by the yellow enzyme of Warburg) [Banga, 1937, 1, 2; Laki, 1937], and dehydrogenated back to OAA by malic dehydrogenase. Apart from the hydrogenation to l-malic acid, the aqueous solution of OAA spontaneously decomposes slowly into pyruvic acid (referred to as PUA in this paper) and C02, and in tissues it undergoes several other reactions. Decarboxylation of OAA is increased in presence of either surviving or heated tissue.

Which way does the citric acid cycle turn during hypoxia? The critical role of α‐ketoglutarate dehydrogenase complex

“…Ironically, Krebs himself was proving his theory on the cycle by fighting opposing views of other researchers who ignored the reversibility of several steps. Below is an excerpt from a reply to the criticisms of F. L. Breusch and of J. Thomas (Breusch, ; Thomas, ):

Several of the criticisms arise solely from a misinterpretation of the theory. Thomas as well as Breusch draw incorrect conclusions from the theory and argue against the theory when these conclusions are not confirmed by their experiments.

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The Intermediary Stages in the Biological Oxidation of Carbohydrate

“…The rate of reaction is somewhat lower in other tissues (29,81). For instance, 0.4 g. muscle suspended in 4 ml.…”

“…It is lower in neutral solutions. Tissue suspensions also catalyze the decomposition (75,76,77,78,29) but as boiled tissue has much the same effect as fresh material, it is very doubtful that the reaction is due to a specific enzyme. Tissue suspensions also catalyze the decomposition (75,76,77,78,29) but as boiled tissue has much the same effect as fresh material, it is very doubtful that the reaction is due to a specific enzyme.…”

“…Formation of Citrate and Related Substances.-When oxaloacetate is added to muscle suspensions, decarboxylation and reduction never account for the total oxaloacetate which disappears (80,29). Under conditionp where the nonenzymic decarboxylation is small, the yield of malate and fumarate does not exceed 75%; it is generally of the order of 50% (81).…”

Pyruvate Metabolism

“…Citrate, cis-aconitate, isocitrate, a-ketoglutarate, succinate, fumarate, malate and oxalacetate, members of either the "citric acid cycle" or the "Cq dicarboxylic acid cycle," have all been reported to increase the respiration of minced muscle, although the accelerating effect of citrate itself has been challenged (18,183,194). Citrate, cis-aconitate, isocitrate, a-ketoglutarate, succinate, fumarate, malate and oxalacetate, members of either the "citric acid cycle" or the "Cq dicarboxylic acid cycle," have all been reported to increase the respiration of minced muscle, although the accelerating effect of citrate itself has been challenged (18,183,194).…”