Studies of intermediary metabolism in germinating pea cotyledons. The pathway of ethanol metabolism and the role of the tricarboxylic acid cycle

Abstract

1. The pathway of ethanol metabolism in cotyledons of 3-day-old pea seedlings has been examined by incubating tissue slices with [1−14C]ethanol and [2−14C]ethanol for periods up to 1hr. 2. Ethanol was rapidly incorporated into citrate and glutamate but relatively small amounts of 14C were present in the evolved carbon dioxide even after 1hr. of ethanol metabolism. 3. Similar data were obtained from experiments in which [1,2−14C2]acetaldehyde and [14C]acetate were supplied. 4. The results are interpreted as indicating that ethanol is metabolized essentially via the reactions of the tricarboxylic acid cycle with a substantial drain of α-oxoglutarate to support the biosynthesis of glutamate. 5. It is concluded that oxaloacetate, required for the incorporation of ethanol into citrate, arises mainly from the transamination of aspartate and the fixation of carbon dioxide.