Folate-dependent enzyme, that displays both transferase and deaminase activity. Serves to channel one-carbon units from formiminoglutamate to the folate pool. 5-formimidoyltetrahydrofolate + L-glutamate = (6S)-5,6,7,8-tetrahydrofolate + N-formimidoyl-L-glutamate 5-formimidoyltetrahydrofolate + 2 H(+) = 5,10-methenyltetrahydrofolate + NH4(+) Amino-acid degradation; L-histidine degradation into L-glutamate; L-glutamate from N-formimidoyl-L-glutamate (transferase route): step 1/1. Homooctamer, including four polyglutamate binding sites. The subunits are arranged as a tetramer of dimers, and form a planar ring-shaped structure. In the C-terminal section; belongs to the cyclodeaminase/cyclohydrolase family. In the N-terminal section; belongs to the formiminotransferase family.