Decapping metalloenzyme that catalyzes the cleavage of the cap structure on mRNAs (PubMed:12417715, PubMed:12218187, PubMed:12923261, PubMed:21070968, PubMed:28002401, PubMed:31875550). Removes the 7-methyl guanine cap structure from mRNA molecules, yielding a 5'-phosphorylated mRNA fragment and 7m-GDP (PubMed:12486012, PubMed:12923261, PubMed:21070968, PubMed:28002401, PubMed:31875550). Necessary for the degradation of mRNAs, both in normal mRNA turnover and in nonsense-mediated mRNA decay (PubMed:14527413). Plays a role in replication-dependent histone mRNA degradation (PubMed:18172165). Has higher activity towards mRNAs that lack a poly(A) tail (PubMed:21070968). Has no activity towards a cap structure lacking an RNA moiety (PubMed:21070968). The presence of a N(6)-methyladenosine methylation at the second transcribed position of mRNAs (N(6),2'-O-dimethyladenosine cap; m6A(m)) provides resistance to DCP2-mediated decapping (PubMed:28002401). Blocks autophagy in nutrient-rich conditions by repressing the expression of ATG-related genes through degradation of their transcripts (PubMed:26098573). a 5'-end (N(7)-methyl 5'-triphosphoguanosine)-ribonucleoside in mRNA + H2O = a 5'-end phospho-ribonucleoside in mRNA + 2 H(+) + N(7)-methyl-GDP Mn(2+) ion is required for highest activity. Can also utilize magnesium ions. Found in a mRNA decay complex with LSM1, LSM3, LSM4, EXOSC2, EXOSC4, EXOSC10, PARN, XRN1, CNOT6, UPF1, UPF2 and UPF3B (PubMed:12417715, PubMed:12515382, PubMed:14527413). Forms a complex with DCP1A, EDC3, DDX6 and EDC4/HEDLS, within this complex directly interacts with EDC4/HEDLS (PubMed:15231747, PubMed:15067023, PubMed:16364915). Interacts with DPC1B (PubMed:15231747). Interacts (via N-terminus and C-terminus) with TRIM21 (via N-terminus and C-terminus) (PubMed:18361920). Associates with polysomes (PubMed:12218187). Interacts with LIMD1, WTIP and AJUBA (PubMed:20616046). Interacts with DDX17 in an RNA-dependent manner (PubMed:21876179). Interacts with ZC3HAV1 (PubMed:21876179). Interacts with APOBEC3G in an RNA-dependent manner (PubMed:16699599). Interacts with ZFP36L1 (via N-terminus) (PubMed:15687258). Interacts with NBDY (PubMed:27918561). Predominantly cytoplasmic, in processing bodies (PB) (PubMed:15273322). A minor amount is nuclear (PubMed:15273322). Expressed in brain and testis. Not detected in heart (at protein level). Phosphorylated at ser-249 in a MTOR-dependent manner (PubMed:26098573). Belongs to the Nudix hydrolase family. DCP2 subfamily.