This domain is found in phage proteins, such as A0A2H5BHG5 from Acinetobacter phage SH-Ab 15497, which are associated with PurZ, an enzyme that catalyses the synthesis of diaminopurine (Z), a DNA modification that gives phages an advantage for evading host restriction enzymes activity [1]. This domain has dATP and dGTP pyrophosphohydrolase activity; it catalyses the hydrolysis of dATP/dGTP to pyrophosphate and dAMP/dGMP, respectively, with little or no activities for NTPs and pyrimidine dNTPs. It is suggested that enzymes containing this domain supply dGMP as the substrate for PurZ, elevating dZTP level to promote Z incorporation [1].

1: A widespread pathway for substitution of adenine by diaminopurine in phage genomes. Zhou Y, Xu X, Wei Y, Cheng Y, Guo Y, Khudyakov I, Liu F, He P, Song Z, Li Z, Gao Y, Ang EL, Zhao H, Zhang Y, Zhao S; Science. 2021;372:512-516. PMID:33926954