Studies on yeast metabolism. 3. The intracellular level of pyruvate during yeast fermentation

Abstract

The intracellular pyruvate level of yeast was measured as the difference between the total pyruvate extracted from a suspension by trichloroacetic acid and that excreted into the medium. The relation between fermentation rate and intracellular pyruvate resembles that between the velocity of an enzyme reaction and substrate concentration. The velocity of the carboxylase system in metabolizing yeast suspensions may therefore be deduced from pyruvate measurement when direct measurement by determination of CO2 output is not feasible. A possible interpretation of the results as a direct determination of the kinetics of the carboxylase system in vivo is given. The limitation of fermentation rate, in the yeast studied, by carboxylase is discussed.