Catalyzes the hydrolytic cleavage of the carbon-nitrogen bond in imidazolone-5-propanoate to yield N-formimidoyl-L-glutamate. It is the third step in the universal histidine degradation pathway. 4-imidazolone-5-propanoate + H2O = N-formimidoyl-L-glutamate Binds 1 zinc or iron ion per subunit. Amino-acid degradation; L-histidine degradation into L-glutamate; N-formimidoyl-L-glutamate from L-histidine: step 3/3. Belongs to the metallo-dependent hydrolases superfamily. HutI family.