sentences:  This mutation was first identified by Eloise Giblett, a professor at the University of Washington, in 1975.PNP is a key enzyme in the purine catabolic pathway, and is required for purine degradation.Specifically, it catalyzes the conversion of inosine to hypoxanthine and guanosine to guanine (both guanine and hypoxanthine will be made into xanthine which will then become uric acid).