Sorbose counterflow as a measure of intracellular glucose in baker's yeast.

Wilkins, Peter O. (New Jersey College of Medicine and Dentistry, Jersey City), and Vincent P. Cirillo. Sorbose counterflow as a measure of intracellular glucose in baker's yeast. J. Bacteriol. 90:1605-1610. 1965.-The intracellular concentration of glucose in metabolizing baker's yeast was determined indirectly from the glucose-induced counterflow of previously accumulated sorbose. The method is based on the concept that sugar transport in yeast is a symmetrical facilitated diffusion. The intracellular glucose concentration increased with an increase in the extracellular concentration and was higher in aerobiosis than in anaerobiosis. The concentrations were considerably greater than those obtained by direct analysis of intracellular glucose. Calculation of the apparent maximal velocity of glucose transport yielded values which varied with the rate of metabolism and the extracellular concentration. This suggests that during glucose metabolism the transport of hexoses includes elements that are not revealed by experiments involving metabolic inhibitors or nonmetabolizable sugars.