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Methanopterin

Tetrahydromethanopterin
Tetrahydromethanopterin.svg
Identifiers
3D model (Jmol)
ChemSpider
PubChem CID
Properties
C
30
H
45
N
6
O
16
P
Molar mass 776.682661
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Tetrahydromethanopterin (THMPT, H
4
MPT
) 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.

Tetrahydrosarcinapterin (THSPT, H
4
SPT
) is a modified form of THMPT, wherein a glutamyl group linked to the 2-hydroxyglutaric acid terminus.

N-Formylmethanofuran donates the C1 group to the N5 site of the pterin to give the formyl- THMPT. The formyl group subsequently condenses intramolecularly to give methenyl- THMPT+
, which is then reduced to methylene- THMPT. 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 methyl donor to coenzyme M, a conversion mediated by methyl- THMPT:coenzyme M methyl-transferase.

THMPT is related to the better known tetrahydrofolic acid (THFA, H
4
FA
). 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 hydrogenases that do contain Fe-S cluster.


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