Different affinities of the -and -anomers of D-glucose, D-mannose and D-xylose for the glucose uptake system of baker's yeast.

Abstract

A recording technique for measuring the sugar uptake by cell suspensions using a polarimeter is described. The method makes it possible to calculate the uptake rates of the α-and β-anomers. The constitutive monosaccharide transport system ofSaccharomyces cerevisiae andSaccharomyces fragilis exhibits a higher affinity for the α-anomers ofd-glucose,d-manose andd-xylose than for the corresponding β-anomers, this resulting in a preferential uptake of the α-anomers from a mixture. The α-anomer ofd-xylose is preferred both during influx and efflux. The membrane transport ofd-xylose inSaccharomyces cerevisiae is not associated with a change of the anomer configuration. The facilitated diffusion system appears to possess a regulatory role for the utilization ofd-glucose andd-mannose in both yeast species investigated.