5 Regulation of Carbon and Phosphate Utilization

Abstract

I. INTRODUCTION The ability of yeasts to utilize various carbon and phosphate sources is highly regulated: Expression of genes for utilization of certain carbon sources is induced by these carbon sources, and levels of enzymes for utilization of poor carbon and phosphate sources are usually decreased when a better source is available. Because of their tight regulation, the genes encoding such enzymes (most notably those for galactose and organic phosphate utilization) have long been a central focus of studies on gene regulation in Saccharomyces cerevisiae (for review, see Oshima 1982). These analyses have provided a wealth of information on mechanisms of gene regulation that we review in this chapter. Our discussion is limited to studies of S. cerevisiae and its close relatives. Two aspects of the regulation of genes for carbohydrate utilization are considered. First, we describe what is known about regulatory mechanisms specific to genes responsible for the utilization of particular sugars. Second, we review what is known about glucose (carbon catabolite) repression, an important global regulatory mechanism that affects most genes involved in carbon metabolism. These regulatory mechanisms are compared to those responsible for repression by inorganic phosphate of genes for organic phosphate utilization. We emphasize work reported since the publication of the previous volumes of this series. Due to space constraints, we have been unable to provide exhaustive references. We attempted to survey comprehensively the relevant literature through June 1990, but were able to include only key references published from that time through March 1992. II. UTILIZATION...