Involved in polyamine biosynthesis. 2 H(+) + H2O + N-carbamoylputrescine = CO2 + NH4(+) + putrescine Amine and polyamine biosynthesis; putrescine biosynthesis via agmatine pathway; putrescine from N-carbamoylputrescine (amidase route): step 1/1. Homooctamer. Belongs to the carbon-nitrogen hydrolase superfamily.