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 with a lower affinity for dUTP than for dCTP. dCTP + 2 H2O = diphosphate + dUMP + NH4(+) Inhibited by dTTP. Optimum pH is 7.5. Retains over 70% of its activity after heating at 90 degrees Celsius for 10 min. Pyrimidine metabolism; dUMP biosynthesis; dUMP from dCTP: step 1/1. Homotrimer (PubMed:12756253, PubMed:12909016). Two trimers assemble into a hexamer by stacking on top of each other (PubMed:12909016). Belongs to the dCTP deaminase family.