The function of HPRT1 (hypoxanthine phosphoribosyltransferase 1, Ensembl gene identifier ENSG00000165704) is as follows. Converts guanine to guanosine monophosphate, and hypoxanthine to inosine monophosphate. Transfers the 5-phosphoribosyl group from 5- phosphoribosylpyrophosphate onto the purine. Plays a central role in the generation of purine nucleotides through the purine salvage pathway.