Reserve carbohydrates metabolism in the yeast Saccharomyces cerevisiae

Glycogen and trehalose are the two glucose stores of yeast cells. The large variations in the cell content of these two compounds in response to diffe rent environmental changes indicate that their metabolism is controlled by complex regulatory systems. In this review we present information on the re gulation of the activity of the enzymes implicated in the pathways of synth esis and degradation of glycogen and trehalose as well as on the transcript ional control of the genes encoding them, cAMP and the protein kinases Snf1 and Pho85 appear as major actors in this regulation. From a metabolic poin t of view, glucose-6-phosphate seems the major effector in the net synthesi s of glycogen and trehalose. We discuss also the implication of the recentl y elucidated TOP-dependent nutrient signalling pathway in the control of th e yeast glucose stores and its integration in growth and cell division. The unexpected roles of glycogen and trehalose found in the control of glycoly tic flux, stress responses and energy stores for the budding process, demon strate that their presence confers survival and reproductive advantages to the cell. The findings discussed provide for the first time a teleonomic va lue for the presence of two different glucose stores in the yeast cell. (C) 2001 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.