HPT1 encodes hypoxanthine-guanine phosphoribosyltransferase, an enzyme involved in the salvage pathway of purine nucleotide biosynthesis (1). Hpt1p catalyzes the conversion of the purine bases hypoxanthine and guanine to the nucleotides IMP and GMP (4). The enzyme functions as a dimer and can be inhibited in vitro by its end-product GMP (5, 6). In hpt1 null mutants, if the de novo pathway of guanine nucleotide biosynthesis is blocked, either through mutation of ade2 or by the addition of mycophenolic acid, cells are unable to grow even with the addition of guanine to the media (1, 2). Null mutants are also resistant to the hypoxanthine/guanine analog 8-azaguanine as well as to the anti-cancer drug cisplatin (1, 7). In humans, partial and complete deficiencies of the HPT1 ortholog HPRT1 (OMIM) are associated with the genetic disorders HPRT-related gout/Kelley-Seegmiller syndrome (OMIM) and Lesch-Nyhan syndrome (OMIM), respectively (2 and references therein).

Last updated: 2006-09-18