5,10-Methenyl-5,6,7,8-tetrahydromethanopterin, a One-Carbon Carrier in the Process of Methanogenesis

5,10-Methenyl-5,6,7,8-tetrahydromethanopterin was isolated from Methanobacterium thermoautotrophicum. The structure of this compound was elucidated by various two-dimensional nuclear magnetic resonance techniques and confirmed by fast atom bombardment mass spectrometry. The structure of 5,10-methenyl-5,6,7,8-tetrahydromethanopterin shows one additional carbon atom as compared to the parent compound methanopterin. This additional carbon atom is rapidly labeled in vivo by 13C02. It is shown that 5,10- methenyl-5,6,7,8-tetrahydromethanopterin is a physiologically active one-carbon carrier at the formyl level of oxidation in the methanogenic pathway from C02.