Bifunctional enzyme that catalyzes both the deamination of dCTP to dUTP and the hydrolysis of dUTP to dUMP without releasing the toxic dUTP intermediate. It also acts as a dUTP diphosphatase. Affinity for dCTP and dUTP are very similar. dCTP + 2 H2O = diphosphate + dUMP + NH4(+) dTTP inhibits both the combined reaction and the dUTPase reaction. kcat is 0.18 sec(-1) with dCTP as substrate. kcat is 0.33 sec(-1) with dUTP as substrate. Pyrimidine metabolism; dUMP biosynthesis; dUMP from dCTP: step 1/1. Homotrimer. Belongs to the dCTP deaminase family.