Decapping scavenger enzyme that catalyzes the cleavage of a residual cap structure following the degradation of mRNAs by 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 10 nucleotide substrates (small capped oligoribonucleotides) and specifically releases 5'-phosphorylated RNA fragments and 7-methylguanosine monophosphate (m7GMP) or tri-methyl guanosine nucleoside monophosphate (m3(2,2,7)GMP), respectively. Does not hydrolyze unmethylated cap analog (GpppG) and shows no decapping activity on intact m7GpppG-capped mRNA molecules longer than 25 nucleotides. 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 DCS1 to m7GMP (PubMed:14523240). Binds to m7GpppG and strongly to m7GDP. May also regulate the 5'->3' exoribonucleolytic mRNA decay pathway in a cap-independent manner. Negatively regulates trehalase activity. 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 The hydrolytic product 7-methylguanosine diphosphate (m7GDP) efficiently inhibits the decapping scavenger activity and acts as a competitive inhibitor in vitro. kcat is 0.012 sec(-1) with m7GpppG as substrate (homodimer). kcat is 0.0015 sec(-1) with m7GpppG as substrate (heterodimer). kcat is 0.0017 sec(-1) with m7GDP as substrate (homodimer). kcat is 0.0005 sec(-1) with m7GDP as substrate (heterodimer). The homodimer catalytic efficiency with m7GpppG is at least 8-fold higher than with the heterodimer. The homodimer catalytic efficiency with m7GDP is at least 3.4-fold higher than with the heterodimer. Homodimer. Forms heterodimer with DCS2; the interaction inhibits the DCS1 scavenger decapping activity during post-diauxic growth. Predominantly cytoplasmic. By nutrient, osmotic, oxidative and heat stress. Up-regulated during the diauxic shift. The C-terminal histidine triad (HIT) motif and the N-terminal domain are required for the decapping activity. Phosphorylated. Phosphorylation occurs upon glucose deprivation. Present with 9920 molecules/cell in log phase SD medium. Belongs to the HIT family.