Isolation and Characterization of the Saccharomyces cerevisiae XPT1 Gene Encoding Xanthine Phosphoribosyl Transferase

A new Saccharomyces cerevisiae gene, XPT1, was isolated as a multicopy suppressor of a hypoxanthine phosphoribosyl transferase (HPRT) defect. Disruption of XPT1 affects xanthine utilization in vivo and results in a severe reduction of xanthine phosphoribosyl transferase (XPRT) activity while HPRT is unaffected. We conclude that XPT1 encodes XPRT in yeast.