InterPro

Ribose-phosphate diphosphokinase, also known as ribose-phosphate pyrophosphokinase (RPPK), or phosphoribosyldiphosphate synthetase (EC:2.7.6.1), catalyses the transfer of an intact diphosphate (PP) group from ATP to ribose-5-phosphate (R-5-P), which results in the formation of AMP and 5-phospho-D-ribosyl--1-diphosphate (PRPP).

PRPP is an essential precursor for purine and pyrimidine nucleotides, both in the de novo synthesis and in the salvage pathway, as well as in the synthesis of pyridine nucleotide coenzymes. The activity of PPPK is highly regulated. Besides competitive inhibition at the substrate binding sites, most RPPKs are regulated in an allosteric manner, in which ADP generally acts as the most potent inhibitor. In some systems, close homologues lacking enzymatic activity exist and perform regulatory functions.