GTP cyclohydrolase activity GTP cyclohydrolase IV activity https://github.com/geneontology/go-ontology/issues/26710 https://github.com/geneontology/go-ontology/issues/30193 Catalysis of the reaction: GTP + H2O = 7,8-dihydroneopterin 2',3'-cyclic phosphate + diphosphate + formate + H+. This activity is part of the biosynthesis of methanopterin in Archaea, and requires Fe2+. MptA activity jl EC:3.5.4.39 RHEA:25860 GO:0044682 Fe(2+)-dependent archaeal-specific GTP cyclohydrolase activity archaeal-specific GTP cyclohydrolase activity molecular_function 2012-08-15T11:18:40Z