Affinity and capacity of the glucose carrier in different physiological states of a synchronous culture of baker's yeast.

Abstract

A Saccharomyces cerevisiae culture was synchronized by a cell size selection and a temperature shock and cells grown (a) in 0.166m glucose for 0, 60 and 120 min to obtain different morphological stages of the culture, and (b) in 0.166m and 0.0166m glucose and in 0.178m sodium lactate, to achieve different degrees of aerobic metabolism. The metabolic parameters\((\mathop Q\nolimits_{O_2 }^{O_2 } , \mathop Q\nolimits_{CO_2 }^{O_2 } \mathop Q\nolimits_{CO_2 }^{Argon} and RQ)\), the maximum rate of glucose uptake, the maximum rate of d-xylose efflux and the apparent Michaelis constant for d-glucose were determined for the various cultures. It was found that highly aerobic cells with a lowRQ (in particular the lactate-grown ones) showed a decreased capacity for sugar transport and a lower affinity for glucose uptake. The connection of these properties with the Pasteur effect is discussed.