Phosphoribosyl Pyrophosphate Synthetase Associated Protein 1 (PRPSAP1)

Phosphoribosylpyrophosphate (PRPP) synthetase catalyzes the formation of PRPP from ATP and ribose 5-phosphate. Ishizuka et al. (1996) noted that the rat liver enzyme exists as complex aggregates of 34-, 39-, and 41-kD components, with the 34-kD species being the catalytic subunit. The 34-kD subunit from rat liver is a mixture of 2 highly homologous isoforms, PRS I and PRS II. The PRS I and PRS II mRNAs are encoded by 2 distinct genes, designated Prps1 and Prps2. The human PRPS1 and PRPS2 genes are located in different regions of the X chromosome, Xq22-q24 and Xp22.3-p22.2, respectively. The deduced 356-amino acid human protein shares 98% identity with rat Pap39 and 44% identity with human PRS I and PRS II. Northern blot analysis revealed that PAP39 was expressed as a 2.2-kb mRNA in all human tissues tested.