In enzymology, a nucleotide diphosphatase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are dinucleotide and H<sub>2</sub>O, whereas its product is mononucleotide.
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 dinucleotide nucleotidohydrolase. Other names in common use include nucleotide pyrophosphatase, and nucleotide-sugar pyrophosphatase. This enzyme participates in 5 metabolic pathways: purine metabolism, starch and sucrose metabolism, riboflavin metabolism, nicotinate and nicotinamide metabolism, and pantothenate and coa biosynthesis.
, 5 structures have been solved for this class of enzymes, with PDB accession codes , , , , and .