Accumulation of uric acid and decreased activities of enzymes involved in the purine salvage pathway, such as purine nucleoside phosphorylase (PNP) and hypoxanthine-guanine phosphoribosyl transferase (HGPRT), are related with metabolic disorders including hyperuricemia, gout, immunological disorders, neurologic abnormalities and Lesch-Nyhan syndrome, some of which are known to cause early death in humans (Fox, 1981; Curto et al., 1998; Skinner et al., 2006; Torres and Puig, 2007; Jurecka, 2009). Here, HPRT1 is linked to metabolic disease.