title: Purification and properties of the 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanobacterium thermoautotrophicum.
abstract: The 5,10-methenyltetrahydromethanopterin cyclohydrolase of Methanobacterium thermoautotrophicum was purified 128-fold to homogeneity. The enzyme had a subunit Mr of 41,000 as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. From high-performance size exclusion chromatography of the native protein, an Mr of 82,000 was determined, suggesting a dimer of identical subunits. The enzyme was inhibited by 10-formyltetrahydromethanopterin and stimulated by Mg2+. Evaluation of the reaction equilibrium indicated that the methenyl derivative was favored over 5-formyltetrahydromethanopterin, with a much higher equilibrium constant than for the analogous reaction of tetrahydrofolate derivatives. Folate derivatives did not serve as substrates for this enzyme.
mesh_terms: D000619:Aminohydrolases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D019605:Euryarchaeota / Q000201:enzymology*; D005492:Folic Acid / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity
chemical_list: D005492:Folic Acid; D000619:Aminohydrolases; C050675:methenyltetrahydromethanopterin cyclohydrolase