MUTATION ADE13-1 IN THE YEAST SACCHAROMYC ES-CEREVISIAE INHIBITS GROWTH ON THE COMPLETE MEDIUM WITH GLUCOSE AND EPISTATICALLY INTERACTS WITH MUTATIONS IN OTHER GENES FOR PURINE BIOSYNTHESIS

Saccharomyces cerevisiae gene ADE13 encodes enzyme adenylosuccinate ly ase catalyzing steps 8 and 12 of the de novo purine pathway. The mutat ion ade13-1 induced by ethyl methanesulfonate leads to a complete loss of enzymatic activity. Stocks with this mutation cannot grow on compl ete organic media with glucose or fructose as a carbon source, but the y can grow on media with glycerol or ethanol. The inhibiting effect of glucose is confirmed by the lack of growth on the medium with glycero l instead of glucose. Three independently obtained ade2 mutations and mutations ade1-p3, ade4, ade5, and ade5,7-33 suppress growth inhibitio n by glucose; i.e., they are epistatic with respect to this phenotypic al expression of mutation ade13-1. The activity of adenylsuccinate lya se is not reconstituted. Mutations ade1-263, ade6, ade7-23, and ade8-2 1 do not manifest an epistatic effect. It was suggested that purine sy nthesis genes participate in the control of glycolysis or in the trans duction of signal about the carbon source in the medium. The propertie s of ade mutations found by us were previously unknown. The results of our study contribute to the knowledge about the function of purine sy nthesis genes in yeasts.