Decapping scavenger enzyme that catalyzes the cleavage of a residual cap structure following the degradation of mRNAs of the 3'->5' exosome-mediated mRNA decay pathway. Hydrolyzes cap analog structures like 7-methylguanosine nucleoside triphosphate (m7GpppG) and tri-methyl guanosine nucleoside triphosphate (m3(2,2,7)GpppG) with up to 2 nucleotide substrates (small capped oligoribonucleotides) and specifically releases 5'-phosphorylated RNA fragments and 7-methylguanosine monophosphate (m7GMP). Does not hydrolyze unmethylated cap analog (GpppG) and shows no decapping activity on intact m7GpppG-capped mRNA molecules. Does not hydrolyze 7-methylguanosine diphosphate (m7GDP) and tri-methylguanosine diphosphate (m3(2,2,7)GDP) to m(7)GMP and m3(2,2,7)GMP, respectively (PubMed:22985415). May also play a role in the 5'->3 mRNA decay pathway; m7GDP, the downstream product released by the 5'->3' mRNA mediated decapping activity, may be also converted by dcs-1 to m7GMP. Binds to m7GpppG and strongly to m7GDP. a 5'-end (N(7)-methyl 5'-triphosphoguanosine)-ribonucleoside in mRNA + H2O = a 5'-end diphospho-ribonucleoside in mRNA + 2 H(+) + N(7)-methyl-GMP a 5'-end (N(2),N(2),N(7)-trimethyl 5'-triphosphoguanosine)-(ribonucleoside) in mRNA + H2O = (N(2),N(2),N(7))-trimethyl-GMP + a 5'-end diphospho-ribonucleoside in mRNA + 2 H(+) The hydrolytic product 7-methylguanosine diphosphate (m7GDP) efficiently inhibits the decapping scavenger activity and acts as a competitive inhibitor in vitro. kcat is 0.174 sec(-1) with m7GpppBODIPY as substrate. The catalytic efficiency with m7GpppBODIPY is at least 35- to 75-fold higher than with ApppBODIPY and GpppBODIPY as substrates, respectively. Expressed in neurons in the ventral cord, the nerve ring and the pharynx. Expressed in the embryo during all developmental stages. Up-regulated by heat schock. Belongs to the HIT family.