Catalyzes the synthesis of phosphoribosylpyrophosphate (PRPP) that is essential for nucleotide synthesis. {ECO:0000269|PubMed:16939420, ECO:0000269|PubMed:17701900, ECO:0000269|PubMed:7593598}. This is the function of ENSG00000147224 (PRPS1, phosphoribosyl pyrophosphate synthetase 1).