In enzymology, a phosphoribosyl-ATP diphosphatase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are 1-(5-phosphoribosyl)-ATP and H<sub>2</sub>O, whereas its two products are 1-(5-phosphoribosyl)-AMP and diphosphate.
This enzyme participates in histidine metabolism. It employs one cofactor, H+.
This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is 1-(5-phosphoribosyl)-ATP diphosphohydrolase. Other names in common use include phosphoribosyl-ATP pyrophosphatase, and phosphoribosyladenosine triphosphate pyrophosphatase.