Hydrolyzes ureidoacrylate to form aminoacrylate and carbamate. The carbamate hydrolyzes spontaneously, thereby releasing one of the nitrogen atoms of the pyrimidine ring as ammonia and one of its carbon atoms as CO2. (Z)-3-ureidoacrylate + H(+) + H2O = (Z)-3-aminoacrylate + CO2 + NH4(+) (Z)-3-ureidoacrylate + H2O = (Z)-3-aminoacrylate + carbamate + H(+) (Z)-2-methylureidoacrylate + H(+) + H2O = (Z)-2-methylaminoacrylate + CO2 + NH4(+) Belongs to the isochorismatase family. RutB subfamily. Extended N-terminus.