Decapping metalloenzyme that catalyzes the cleavage of the cap structure on mRNAs. Removes the 7-methyl guanine cap structure from mRNA molecules, yielding a 5'-phosphorylated mRNA fragment and 7m-GDP. Necessary for the degradation of mRNAs, both in normal mRNA turnover and in nonsense-mediated mRNA decay. Plays a role in replication-dependent histone mRNA degradation. Has higher activity towards mRNAs that lack a poly(A) tail. Has no activity towards a cap structure lacking an RNA moiety. 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. Blocks autophagy in nutrient-rich conditions by repressing the expression of ATG-related genes through degradation of their transcripts. 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. Forms a complex with DCP1A, EDC3, DDX6 and EDC4/HEDLS, within this complex directly interacts with EDC4/HEDLS. Interacts with DPC1B, UPF1, UPF2 and UPF3B. Associates with polysomes. Interacts (via N-terminus and C-terminus) with TRIM21 (via N-terminus and C-terminus). Interacts with LIMD1, WTIP and AJUBA. Interacts with DDX17 in an RNA-dependent manner. Interacts with ZC3HAV1. Interacts with APOBEC3G in an RNA-dependent manner. Interacts with ZFP36L1 (via N-terminus). Interacts with NBDY. Predominantly cytoplasmic, in processing bodies (PB). A minor amount is nuclear. Belongs to the Nudix hydrolase family. DCP2 subfamily.