Location of trehalase and trehalose in yeast cells

Abstract

Analysis of the cellular distribution of trehalase and trehalose in baker's yeast reveals trehalase to be located in the soluble fraction of lysates prepared from protoplasts; the bulk of the substrate remains associated with the particulate fraction. Neither trehalose nor trehalase can be detected in the cell-wall digest. The cytoplasmic membrane thus seems to be a barrier between enzyme and substrate. Alteration of its permeability, in the presence of toluene or during cell division, leads to hydrolysis of trehalose by trehalase. The enzyme is present during all phases of the growth curve, although its specific activity decreases when the rate of trehalose synthesis is maximal. An effect of exogenous glucose on trehalase activity levels is demonstrated, as well as the influence of glucose levels upon utilization of exogenous trehalose. The rate of exogenous trehalose utilization by protoplasted cells, which still contain trehalase, is equivalent to that of intact cells; thus the existence of a permeability barrier to trehalose at the cell wall seems to be excluded.