Formaldehyde activation factor, tetrahydromethanopterin, a coenzyme of methanogenesis

Open Access
Publisher Website
Google Scholar
Abstract
An oxygen-labile formaldehyde activation factor (FAF) was isolated in highly purified form by use of anoxic fractionation procedures. The molecular weight of FAF was determined to be 776 and that of methanopterin (MPT) 772 by fast-atom-bombardment mass spectrometry (FABMS). High-resolution FABMS measurements on MPT and FAF indicated molecular formulas of C30H41N6O16P and C30H45N6O16P, respectively. The presence of phosphorus was confirmed by 100-MHz 31P NMR. The 360-MHz 1H NMR spectrum of FAF in deuterium oxide was similar to that of MPT. A functional relationship between MPT and FAF was documented; both compounds stimulated the reductive demethylation of 2-(methylthio)ethanesulfonic acid (CH3-S-CoM) to CH4 when formaldehyde oxidation provided a source of electrons, and FAF replaced MPT in the CH3-S-CoM-stimulated conversion of CO2 to CH4 under H2 (the RPG effect). MPT was enzymically converted to FAF during the reduction of CH3-S-CoM, and HCHO to CH4 under H2. Evidence indicates that FAF is tetrahydromethanopterin.