3.5.4.27 methenyltetrahydromethanopterin cyclohydrolase; 5,10-methenyltetrahydromethanopterin cyclohydrolase; N5,N10-methenyltetrahydromethanopterin cyclohydrolase; methenyl-H4MPT cyclohydrolase; 5,10-methenyltetrahydromethanopterin 10-hydrolase (decyclizing • • •