Isolation and characterization of the Saccharomyces cerevisiae XPT1 gene encoding xanthine phosphoribosyl transferase

Both hypoxanthine phosphoribosyl transferase (HPRT) and xanthine phosphoribosyl transferase XPRT activities from the wild-type and isogenic Saccharomyces cerevisiae XPT1 gene were assayed in crude extracts using 8-3H hypoxanthine and 14C xanthine as substrates. The HPRT activity was observed to the same in both the wild type and in the xpt1 strain. However, the XPRT activity in the xpt1 disrupted strain was 6% lesser than in the wild-type. These results suggest that XPT1 encodes XPRT in yeast.