methanofuran

Methanofuran (MF) is a specialized, low-molecular-weight coenzyme used by many methanogenic archaea. It functions as a formyl carrier in the early steps of methanogenesis, accepting a formyl group to form formyl-methanofuran (formyl-MF). The formyl group is subsequently transferred from MF to tetrahydromethanopterin (H4MPT), initiating a series of reactions that convert CO2 or formate into methane.

In this pathway, the formyl group on formyl-MF is transferred to H4MPT by a formyltransferase, producing formyl-H4MPT. Through a sequence of reductions and rearrangements, formyl-H4MPT is converted to methenyl-H4MPT and eventually to the methylated carrier that participates in the final reduction to methane. The final reduction to methane involves coenzyme M and coenzyme B.

MF is found in a broad range of methanogenic archaea, including orders Methanobacteriales, Methanococcales, and Methanomicrobiales. It is not known to be used by bacteria or eukaryotes. The molecule is synthesized de novo in methanogens and is distinct from folate-based cofactors used in other domains of life.

Understanding MF biology helps elucidate how methanogens fix carbon and conserve energy during methane production. The MF system interacts with other cofactors such as coenzyme F420 and coenzyme M, and its study informs biotechnological approaches to methane generation and archaeal metabolism.