The in vitro oxidation of pyruvic and α-ketobutyric acids by ground preparations of pigeon brain. The effect of inorganic phosphate and adenine nucleotide

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Abstract
Inorganic phosphate is required for the oxidation of pyruvic and [alpha]-ketobutyric acids, both aerobically with a dialysed pigeon brain suspension, and anaerobically with a pigeon brain [alpha]-keto-acid dehydrogenase with methylene blue as H-acceptor. Arsenate can replace phosphate only in the latter case. [alpha]-Ketobutyrate is oxidised at the same rate by minced and by ground pigeon brain; the R.Q. (2.38) and O2/[alpha]-ketobutyrate ratio (0.41) are similar for the 2 preps. The rate of oxidation of [alpha]-ketobutyrate is unaffected by adenine nucleotide, except after prolonged dialysis of the brain suspension. Pyruvate oxidation, however, is very susceptible to adenine nucleotide catalysis, the O2 uptake, pyruvate utilization and O2/pyruvate ratio all being markedly increased, while the R.Q. is lowered. If that part of the pyruvate oxidation which is specifically catalysed by adenine nucleotide be considered separately, then the following values obtain; O2/pyruvate ratio, 1.20; R.Q., 1.50; gaseous CO2 production/bicarbonate CO2 production, 2.0. Using these figures it has been argued that the utilization of 5 mol. pyruvate requires 6 mol. O2, the products being 9 mol. CO2 and 2 equiv. fixed acid, composition unknown.

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