mRNA decapping enzyme that specifically removes the nicotinamide adenine dinucleotide (NAD) cap from a subset of mRNAs by hydrolyzing the diphosphate linkage to produce nicotinamide mononucleotide (NMN) and 5' monophosphate mRNA (PubMed:25533955, PubMed:27561816, PubMed:27428510). The NAD-cap is present at the 5'-end of some mRNAs and stabilizes RNA against 5'-processing (PubMed:25533955). Has preference for mRNAs with a 5'-end purine (PubMed:27428510). Catalyzes the hydrolysis of a broad range of dinucleotide pyrophosphates, but uniquely prefers the reduced form of NADH (PubMed:7829480, PubMed:25533955). a 5'-end NAD(+)-phospho-ribonucleoside in mRNA + H2O = a 5'-end phospho-adenosine-phospho-ribonucleoside in mRNA + beta-nicotinamide D-ribonucleotide + 2 H(+) H2O + NAD(+) = AMP + beta-nicotinamide D-ribonucleotide + 2 H(+) H2O + NADH = AMP + 2 H(+) + reduced beta-nicotinamide D-ribonucleotide Divalent metal cations. Mg(2+) or Mn(2+). Binds 1 zinc ion per subunit. Optimum pH is 8.5. Homodimer. Belongs to the Nudix hydrolase family. NudC subfamily.