Members of this family are are ring-opening amidohydrolases, including cyanuric acid amidohydrolase (EC 3.5.2.15) (AtzD and TrzD) and barbiturase. Note that barbiturase does not act as defined for EC 3.5.2.1 (barbiturate + water = malonate + urea) but rather catalyzes the ring-opening of barbituric acid to ureidomalonic acid (see Soong, et al., ).