Human dCTP pyrophosphatase 1 (DCTPP1) is a cytosolic enzyme able to hydrolyse deoxynucleoside triphosphates (dNTPs) to their corresponding nucleoside monophosphates. DCTPP1 probably plays a role in protecting DNA or RNA against the incorporation of modified nucleotide triphosphates. Based on mouse studies, Dctpp1 has strong preference for modified dCTPs, with highest activity shown towards 5-iodo-dCTP (5idCTP) (Nonaka et al. 2009). Crystal structures of mouse Dctpp1 suggest it functions as a homotetramer and requires two or three Mg2+ ions per subunit (Wu et al. 2007).