Tetrahydromethanopterin (THMPT, H 4MPT) is a coenzyme in methanogenesis. It is the carrier of the C1 group as it is reduced to the methyl level, before transferring to the coenzyme M.[1]
THMPT is related to the better known tetrahydrofolic acid (THFA, H 4FA). The most important difference between THMPT and THFA is that THFA has an electron-withdrawing carbonyl group on the phenyl ring. As a consequence, methenyl- THMPT is more difficult to reduce than methenyl- THFA. Reduction is effected by a so-called iron-sulfur cluster free hydrogenase.[3] The cumbersome name distinguishes this hydrogenase from the so-called Fe-only hydrogenases that do contain Fe-S cluster.
^Acharya P, Warkentin E, Ermler U, Thauer RK, Shima S (March 2006). "The structure of formylmethanofuran: tetrahydromethanopterin formyltransferase in complex with its coenzymes". J. Mol. Biol. 357 (3): 870–9. doi:10.1016/j.jmb.2006.01.015. PMID16466742.