Decapping enzyme for NAD-capped RNAs: specifically hydrolyzes the nicotinamide adenine dinucleotide (NAD) cap from a subset of RNAs by removing the entire NAD moiety from the 5'-end of an NAD-capped RNA (PubMed:28283058, PubMed:32374864). The NAD-cap is present at the 5'-end of some RNAs and snoRNAs (PubMed:28283058). In contrast to the canonical 5'-end N7 methylguanosine (m7G) cap, the NAD cap promotes mRNA decay (PubMed:28283058). Preferentially acts on NAD-capped transcripts in response to environmental stress (By similarity). Also acts as a non-canonical decapping enzyme that removes the entire cap structure of m7G capped or incompletely capped RNAs and mediates their subsequent degradation (PubMed:23523372, PubMed:28283058). Specifically degrades pre-mRNAs with a defective 5'-end m7G cap and is part of a pre-mRNA capping quality control (PubMed:23523372). Has decapping activity toward incomplete 5'-end m7G cap mRNAs such as unmethylated 5'-end-capped RNA (cap0), while it has no activity toward 2'-O-ribose methylated m7G cap (cap1) (PubMed:23523372). In contrast to canonical decapping enzymes DCP2 and NUDT16, which cleave the cap within the triphosphate linkage, the decapping activity releases the entire cap structure GpppN and a 5'-end monophosphate RNA (PubMed:23523372). Also has 5'-3' exoribonuclease activities: The 5'-end monophosphate RNA is then degraded by the 5'-3' exoribonuclease activity, enabling this enzyme to decap and degrade incompletely capped mRNAs (PubMed:23523372, PubMed:30180947). Also possesses RNA 5'-pyrophosphohydrolase activity by hydrolyzing the 5'-end triphosphate to release pyrophosphates (PubMed:23523372). Exhibits decapping activity towards FAD-capped RNAs (PubMed:32432673, PubMed:32374864). Exhibits decapping activity towards dpCoA-capped RNAs in vitro (PubMed:32432673, PubMed:32374864). a 5'-end NAD(+)-phospho-ribonucleoside in mRNA + H2O = a 5'-end phospho-ribonucleoside in mRNA + H(+) + NAD(+) a 5'-end NAD(+)-phospho-ribonucleoside in snoRNA + H2O = a 5'-end phospho-ribonucleoside in snoRNA + H(+) + NAD(+) a 5'-end (N(7)-methyl 5'-triphosphoguanosine)-ribonucleoside-ribonucleotide in mRNA + H2O = a (N(7)-methyl 5'-triphospho-guanosine)-nucleoside + a 5'-end phospho-ribonucleoside in mRNA + H(+) a 5'-end FAD-phospho-ribonucleoside in mRNA + H2O = a 5'-end phospho-ribonucleoside in mRNA + FAD + H(+) a 5'-end CoA-ribonucleoside in mRNA + H2O = 3'-dephospho-CoA + a 5'-end phospho-ribonucleoside in mRNA + H(+) Binds 2 magnesium ions. The 5'-3' exoribonuclease activity is inhibited by adenosine 3',5'-bisphosphate. Belongs to the DXO/Dom3Z family.