Citric Acid Cycle Activity in Mitochondria Isolated from Mung Bean Hypocotyls

Abstract

Citric acid cycle activity in mitochondria from mung bean (Phaseolus aureus var. Jumbo) hypocotyls were examined by surveying (a) characteristics of oxidation of cycle intermediates; (b) activities of cycle enzymes in mitochondrial extracts; (c) contents of cycle intermediates and electron transport components in isolated mitochondria; and (d) time-course changes of products formed during oxidation of succinate, malate, and citrate. Isolated mitochondria are deficient in thiamine pyro-phosphate and somewhat so in adenylates, but apparently sufficient in CoA, NAD, and electron transport carriers. Cycle activity in the mitochondria is not directly correlated with the activities of the enzymes measured in extracts. These studies led to the conclusion that the region between malate and citrate is an important regulatory area in citric acid cycle functioning in isolated mung bean mitochondria.