IMPDH1 is a rate limiting enzyme in the de novo synthesis of guanine nucleotides and consequently participates in the regulation of cell growth. IMPDH1 takes part in the development of malignancy and the growth progression of some tumors. IMPDH1 performs as a homotetramer to regulate cell growth. IMPDH1 catalyzes the synthesis of xanthine monophosphate(XMP) from inosine-5’’-monophosphate(IMP). Defects in this gene are a cause of retinitis pigmentosa type 10(RP10).