The inhibition of citrate, isocitrate and α-ketoglutarate oxidation in aged potato slices by γ hydroxy α-ketoglutarate

Abstract

The effect of γ hydroxy α-ketogluturate (HKG) was determined on the oxidation of citrate, isocitrate and α-ketoglutarate by aged potato slices. Much as in mitochondrial preparations, HKG was found to inhibit the oxidation of each substrate individually. Acetate utilization was also sharply inhibited by HKG. A comparison of the effect of HKG and of malonate on acetate oxidation established that acetate is respired primarily by way of the tricarboxylic acid cycle in aged potato tissue. Fresh potato slices proved as unable to oxidize isocitrate as citrate, while aged slices oxidized both substrates with equal ease. From the foregoing observation and earlier experiments comparing citrate and α-ketoglutarate metabolism, it is deduced that the block in the tricarboxylic acid cycle in fresh tissue is related to the inhibition or inactivity of isocitric dehydrogenase.