The Utilization by Yeasts of Acids of the Tricarboxylic Acid Cycle

SUMMARY: Growth and respiration on intermediates of the tricarboxylic acid cycle as sole sources of carbon were studied with a number of different yeasts. The incorporation of [1:2-14C]acetate by acetate-respiring cells was studied with yeasts capable of utilizing exogenously supplied cycle intermediates (K +) and also with those unable to do so (K −). Enzyme systems were examined by using cell-free extracts. It was concluded that the difference between K + and K− yeasts was not one of a major metabolic pathway, but probably of the permeability of the intact cells. Evidence was found for the operation of the tricarboxylic acid cycle in yeasts under differing growth conditions, and for the operation of the glyoxylate cycle in yeasts growing on acetate.