Methenyl-tetrahydromethanopterin cyclohydrolase in cell extracts of Methanobacterium

Arch Biochem Biophys. 1985 Nov 1;242(2):430-9. doi: 10.1016/0003-9861(85)90227-9.


Cell extracts of Methanobacterium thermoautotrophicum possess a methenyl-tetrahydromethanopterin (methenyl-H4MPT) cyclohydrolase. The enzyme catalyzes the hydrolysis of methenyl-H4MPT to formyltetrahydromethanopterin (formyl-H4MPT). The reaction is reversible and both the rate and extent of the reaction depend on the pH and the buffer used. Similarly, the nonenzymatic hydrolysis of methenyl-H4MPT is highly dependent on pH and buffer. An active derivative of methenyl-H4MPT was obtained in 94% yield by reacting H4MPT with formic acid in the presence of excess acetic acid under anoxic conditions at 80 degrees C for 3 h. H NMR spectroscopy and fast atom bombardment mass spectrometry revealed the product to be a derivative of methenyl-H4MPT which had lost the alpha-hydroxyglutarylphosphate unit. In spite of this loss, this derivative served both as a substrate for methanogenesis and for the cyclohydrolase. Comparison of the properties of the products of the enzymatic and nonenzymatic hydrolyses indicates that the enzymatic reaction yields N5-formyl-H4MPT whereas the nonenzymatic reaction yields N10-formyl-H4MPT.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aminohydrolases / metabolism*
  • Euryarchaeota / enzymology*
  • Hydrolysis
  • Kinetics
  • Magnetic Resonance Spectroscopy
  • Mass Spectrometry
  • Methenyltetrahydrofolate Cyclohydrolase
  • Spectrophotometry, Ultraviolet


  • Aminohydrolases
  • Methenyltetrahydrofolate Cyclohydrolase