Catalyzes the conversion of N-formimidoyl-L-glutamate to L-glutamate and formamide. H2O + N-formimidoyl-L-glutamate = formamide + L-glutamate Binds 2 manganese ions per subunit. Amino-acid degradation; L-histidine degradation into L-glutamate; L-glutamate from N-formimidoyl-L-glutamate (hydrolase route): step 1/1. Belongs to the arginase family.