Tetrahydromethanopterin (THMPT, ) is a

coenzyme A cofactor is a non-protein chemical compound or Metal ions in aqueous solution, metallic ion that is required for an enzyme's role as a catalysis, catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can ...

methanogenesis Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. It is the fourth and final stage of anaerobic digestion. Organisms capable of producing methane for energy conservation h ...

. It is the carrier of the C1 group as it is reduced to the

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated as ...

level, before transferring to the

coenzyme M Coenzyme M is a coenzyme required for methyl-transfer reactions in the metabolism of archaeal methanogens, and in the metabolism of other substrates in bacteria. It is also a necessary cofactor in the metabolic pathway of alkene-oxidizing bacteria. ...

. Tetrahydrosarcinapterin (THSPT, ) is a modified form of THMPT, wherein a glutamyl group linked to the 2-hydroxy glutaric acid terminus.

THMPT is the main platform for C1 transformations

N-Formyl methanofuran donates the C1 group to the N5 site of the

pterin Pterin is a heterocyclic compound composed of a pteridine ring system, with a " keto group" (a lactam) and an amino group on positions 4 and 2 respectively. It is structurally related to the parent bicyclic heterocycle called pteridine. Pter ...

to give the formyl- THMPT. The formyl group subsequently condenses intramolecularly to give methenyl-, which is then reduced to methylene-THMPT by 5,10-methenyl- hydrogenase with as the electron donor. Methylene- MPT is subsequently converted, using coenzyme F₄₂₀ as the electron source, to methyl-THMPT, catalyzed by F₄₂₀-dependent methylene-THMPT reductase. Methyl-THMPT is the

donor to

, a conversion mediated by methyl-THMPT: coenzyme M methyltransferase.

Comparison with tetrahydrofolic acid

THMPT is related to the better known tetrahydrofolic acid (THFA, ). 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. The cumbersome name distinguishes this hydrogenase from the so-called Fe-only

hydrogenase A hydrogenase is an enzyme that Catalysis, catalyses the reversible Redox, oxidation of molecular hydrogen (H2), as shown below: Hydrogen oxidation () is coupled to the reduction of electron acceptors such as oxygen, nitrate, Ferric, ferric i ...

s that do contain Fe-S cluster.

References

{{Enzyme cofactors Coenzymes Pteridines