The aerobic inhibition of glycolysis associated with brain mitochondria

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Abstract
Two different mechanisms were shown to operate in the reversible aerobic inhibition of glycolysis associated with mitochondrial preparations of rat brain. They can be made to operate separately or together by the choice of suitable experimental conditions. One inhibitory mechanism operates in the system with glucose as substrate in the absence of added ADP and NAD+. This resembles the Pasteur reaction obtained with whole-cell preparations. It is concluded that this form of aerobic inhibition of glycolysis is connected with some process of oxidative phosphorylation. It appears that the NADH-flavoprotein site of oxidative phosphorylation is more important in this connexion than the other 2 sites. Another inhibitory mechanism of glycolysis is the aerobic inhibition of glyceraldehyde phosphate dehydrogenase. This was demonstrated in a system containing fructose diphosphate as the glycolytic substrate with added cofactors; the site of the inhibition was verified by the addition of crystalline glyceraldehyde phosphate dehydrogenase. This form of inhibition is not removed by respiratory inhibitors or by uncouplers of phosphorylation, but can be completely reversed by changing to anaerobic conditions. Glyceraldehyde phosphate dehydrogenase can be protected from aerobic inhibition by 2,3-dimercaptopropanol, but monothiols (glutathione and cysteine) are almost ineffective.