Mediates the hydrolysis of agmatine into N-carbamoylputrescine in the arginine decarboxylase (ADC) pathway of putrescine biosynthesis, a basic polyamine. agmatine + H2O = N-carbamoylputrescine + NH4(+) Inhibited by N-ethylmaleimide and iodoacetamide. Optimum pH is 7.0. Amine and polyamine biosynthesis; putrescine biosynthesis via agmatine pathway; N-carbamoylputrescine from agmatine: step 1/1. Forms homodimers. Belongs to the agmatine deiminase family.