Hydrolyzes deoxynucleoside triphosphates (dNTPs) to the corresponding nucleoside monophosphates. Has a strong preference for dCTP and its analogs including 5-iodo-dCTP and 5-methyl-dCTP for which it may even have a higher efficiency. May protect DNA or RNA against the incorporation of these genotoxic nucleotide analogs through their catabolism. dCTP + H2O = dCMP + diphosphate + H(+) Probably binds two or three Mg(2+) ions per subunit. Inhibited by the reaction end product PPi. Inhibited by dCDP. Inhibited by triptolide. Homotetramer. Expression increases during mitosis (at protein level). Up-regulated by an increase in cellular dCTP pool.