 R5P converts to PRPP, which forces an overproduction of purines, leading to uric acid build up.Accumulation of PRPP is found in Lesch-Nyhan Syndrome.The build up is caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which leads to decreased nucleotide synthesis and an increase of uric acid production.