The uptake of nutrients by yeasts III. The maltose permease of a brewing yeast

Abstract

Listen

Translate article

Maltose penetrates the cells of a brewer's yeast at pH values at which it is not utilized and is finally concentrated in the cells with respect to the medium. The mechanism for concentration is highly specific for maltose as, of a number of sugars and sugar derivatives tested, only methyl α-glucoside at comparatively high concentrations inhibits the uptake of maltose. The mechanism is adaptive in nature and maltose is far more effective as the inducer than any of the other sugars examined, including methyl-α-glucoside. The uptake of maltose by adapted cells is inhibited by various agents, such as dinitrophenol, sodium azide and sodium fluoride, which uncouple the energy supply. Moreover, the aminoacid analogues, p-fluorophenylalanine and β-2-thienylalanine, markedly depress the formation of the concentrating mechanism in the presence of maltose. These findings indicate that the concentration of maltose involves a protein component and that it is brought about by a system resembling both the permeases found in some other microorganisms and the maltotriose permease already demonstrated in the same yeast. The uptake mechanism is therefore called maltose permease.