Kinetics and regulation of fructose and glucose transport systems are responsible for fructophily in Zygosaccharomyces bailii

Abstract

A strain of Zygosaccharomyces bailii was selected for studies on fructose and glucose transport to determine the basis of the fructophilic behaviour of this species. Fructose was transported by a specific low-affinity, high-capacity transport system with a K m of 65.6 mM and a V max of 6.7 mmol g-1 h-1 for cells grown on 2% (w/v) fructose, while the transport of glucose showed a K m of 7 mM and a V max of 1.7 mmol g-1 h-1 for cells grown on 2% (w/v) glucose. The transporter of glucose also fructose as a substrate. Fructose inactivated the glucose transporter; inactivation was faster at higher concentrations. Both transporters were partially inductive. Measurements of metabolic fluxes and respiration and fermentation rates supported the general features identified by transport measurements. The kinetics and regulation of transport of the two sugars confirm the fructophilic behaviour previously described by other authors.