Nucleoside triphosphate pyrophosphatase that hydrolyzes dTTP and UTP. Can also hydrolyze CTP and the modified nucleotides pseudo-UTP, 5-methyl-UTP (m(5)UTP) and 5-methyl-CTP (m(5)CTP). Has weak activity with dCTP, 8-oxo-GTP and N(4)-methyl-dCTP (PubMed:24210219). May have a dual role in cell division arrest and in preventing the incorporation of modified nucleotides into cellular nucleic acids (PubMed:24210219). In addition, the presence of the putative catalytic domain of S-adenosyl-L-methionine binding in the C-terminal region argues for a methyltransferase activity (Probable). dTTP + H2O = diphosphate + dTMP + H(+) H2O + UTP = diphosphate + H(+) + UMP CTP + H2O = CMP + diphosphate + H(+) H2O + psi-UTP = diphosphate + H(+) + psi-UMP H2O + TTP = 5-methyl-UMP + diphosphate + H(+) 5-methyl-CTP + H2O = 5-methyl-CMP + diphosphate + H(+) Pyrophosphatase activity requires a divalent metal cation. kcat is 0.7 sec(-1) with dTTP as substrate. kcat is 0.7 sec(-1) with UTP as substrate. kcat is 0.8 sec(-1) with CTP as substrate. kcat is 0.3 sec(-1) with dCTP as substrate. kcat is 1.5 sec(-1) with m(5)UTP as substrate. kcat is 3.7 sec(-1) with m(5)CTP as substrate. kcat is 2.5 sec(-1) with pseudo-UTP as substrate. kcat is 0.2 sec(-1) with 8-oxo-GTP as substrate. kcat is 0.3 sec(-1) with N(4)-methyl-dCTP as substrate. Homodimer. Widely expressed. In adult, highly expressed in pancreas, placenta, fibroblast, thymus, prostate, testis, ovary and colon. Expressed at lower levels in spleen, small intestine and leukocytes. In fetus, expressed at high levels in the lung and kidney and at lower level in brain and liver. The gene coding for this protein is located in the pseudoautosomal region 1 (PAR1) of X and Y chromosomes. It represents a unique fusion product of 2 different genes of different evolutionary origin and function. The N-terminus is homologous to the bacterial maf/orfE genes and the C-terminus is homologous to ASMT. Exon duplication, exon shuffling and gene fusion seem to be common characteristics of the PAR1 region. In the N-terminal section; belongs to the Maf family. YhdE subfamily. In the C-terminal section; belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family.