NADH pyrophosphatase, a member of the Nudix hydrolase superfamily, catalyzes the cleavage of NADH into reduced nicotinamide mononucleotide (NMNH) and AMP. Like other members of the Nudix family, it requires a divalent cation, such as Mg2+ or Mn2+, for activity. Members of this family are also recognized by the Nudix motif, a highly conserved 23-residue block (GX5EX7REUXEEXGU, where U = I, L or V), that functions as a metal binding and catalytic site. A block of 8 conserved amino acids downstream of the nudix motif is thought to give NADH pyrophosphatase its specificity for NADH. NADH pyrophosphatase forms a dimer.