Biology:Wolfe cycle
The Wolfe Cycle is a methanogenic pathway used by archaea; the archaeon takes H2 and CO2 and cycles them through a various intermediates to create methane.[1] The Wolfe Cycle is modified in different orders and classes of archaea as per the resource availability and requirements for each species, but it retains the same basic pathway.[1] The pathway begins with the reducing carbon dioxide to formylmethanofuran.[1] The last step uses heterodisulfide reductase (Hdr) to reduce heterodisulfide into Coenzyme B and Coenzyme M using Fe4S4 clusters.[1][2] Evidence suggests this last step goes hand-in-hand with the first step, and feeds back into it, creating a cycle.[1] At various points in the Wolfe Cycle, intermediates that are formed are taken out of the cycle to be used in other metabolic processes.[1][3] Since intermediates are being taken out at various points in the cycle, there is also a replenishing (anaplerotic) reaction that feeds into the Wolfe cycle, this is to regenerate necessary intermediates for the cycle to continue.[1] Overall, including the replenishing reaction, the Wolfe Cycle has a total of nine steps.[1] While Obligate [math]\ce{ CO2 }[/math] reducing methanogens preform additional steps to reduce CO2 to [math]\ce{ CH3 }[/math].
Discovery
In 1971, in a review published by Robert Stoner Wolfe, information regarding methanogenesis in M. bryantii was published. The only thing known about this process, at the time, was that Coenzyme M was involved at some point of the pathway.[4] It was though that this was done through a linear cycle. It was not until 1986 that the reduction of [math]\ce{ CO2 }[/math] to [math]\ce{ CH4 }[/math] was proposed as a cycle when it was shown that the Steps 8 and 1 were coupled together.[4]
Steps
The Wolfe Cycle can be run in multiple ways depending on what microbe is using it, multiple pathways are available for different things to be produced. These are a generalized cycle of the Wolfe Cycle.
| steps | reactants | Enzymes[4] | Products used in cycle |
|---|---|---|---|
| 1 | [math]\ce{ CO2 + MF +2H+ }[/math] | Formyl-methanofuran dehydrogenase | [math]\ce{ Formyl - MFR }[/math] |
| 2 | [math]\ce{ N-Formyl - MFR + H4MPT }[/math] | Formyltransferase | [math]\ce{ N-Formyl-H4MPT }[/math] |
| 3 | [math]\ce{ Formyl - H4MPT + H+ }[/math] | methenyl-H4MPT cyclohydrolase | [math]\ce{ methenyl-H4MPT }[/math] |
| 4 | [math]\ce{ Methenyl - H4MPT + F420H2 }[/math] | methylene-H4MPT dehydrogenase | [math]\ce{ methylene-H4MPT }[/math] |
| 5 | [math]\ce{ Methylene - H4MPT + F420H2 }[/math] | methylene-H4MPT reductase | [math]\ce{ methyl-H4MPT }[/math] |
| 6 | [math]\ce{ methyl-H4MPT + HS-CoM }[/math] | methyl-H4MPT/HSCoM methyl transferase | [math]\ce{ CH3-S-CoM }[/math] |
| 7 | [math]\ce{ CH3-S-CoM + HS-CoB }[/math] | methyl-S-CoM reductase | [math]\ce{ CoM-S-S-CoB }[/math] |
| 8 | [math]\ce{ CoM-S-S-CoB + Fdx (ferredoxin) }[/math] | electron bifurcating hydrogenase-heterodisulfide reductase complex | [math]\ce{ Fdx^2- + HS-CoB + HS-CoM }[/math] |
| 9 | [math]\ce{ F420 + H2 + HCO2H }[/math] | F420-reducing hydrogenase | [math]\ce{ CO2 + F420H }[/math] |
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Thauer, Rudolf K. (2012-09-18). "The Wolfe cycle comes full circle" (in en). Proceedings of the National Academy of Sciences 109 (38): 15084–15085. doi:10.1073/pnas.1213193109. ISSN 0027-8424. PMID 22955879. Bibcode: 2012PNAS..10915084T.
- ↑ Wu, Jue; Chen, Shi-Lu (2022-02-18). "Key Piece in the Wolfe Cycle of Methanogenesis: The S–S Bond Dissociation Conducted by Noncubane [Fe 4 S 4 Cluster-Dependent Heterodisulfide Reductase"] (in en). ACS Catalysis 12 (4): 2606–2622. doi:10.1021/acscatal.1c06036. ISSN 2155-5435. https://pubs.acs.org/doi/10.1021/acscatal.1c06036.
- ↑ Vo, Chi Hung; Goyal, Nishu; Karimi, Iftekhar A; Kraft, Markus (January 2020). "First Observation of an Acetate Switch in a Methanogenic Autotroph ( Methanococcus maripaludis S2)" (in en). Microbiology Insights 13: 117863612094530. doi:10.1177/1178636120945300. ISSN 1178-6361. PMID 32843840.
- ↑ 4.0 4.1 4.2 Balch, William E.; Ferry, James G. (2021-01-01), Poole, Robert K.; Kelly, David J., eds., "Chapter One - The Wolfe cycle of carbon dioxide reduction to methane revisited and the Ralph Stoner Wolfe legacy at 100 years", Advances in Microbial Physiology (Academic Press) 79: 1–23, doi:10.1016/bs.ampbs.2021.07.003, PMID 34836609, https://www.sciencedirect.com/science/article/pii/S0065291121000151, retrieved 2023-11-27
 |  |
