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 ${\ce {CO2}}$ reducing methanogens preform additional steps to reduce CO₂ to ${\ce {CH3}}$ .

Discovery

Ralph Stoner Wolfe

Steps:

The Wolfe Cycle can be ran in multiple ways depending on what microbe is using it, multiple pathways are available for different things to be produced. This cycle has a total of fourteen steps.


steps	reactants	Enzymes^[4]	Products used in cycle
1	${\ce {CO2 + MF +2H+}}$	Formyl-methanofuran dehydrogenase	${\ce {Formyl - MFR}}$
2	${\ce {N-Formyl - MFR + H4MPT}}$	Formyltransferase	${\ce {N-Formyl-H4MPT}}$
3	${\ce {Formyl - H4MPT + H+}}$	methenyl-H₄MPT cyclohydrolase	${\ce {methenyl-H4MPT}}$
4	${\ce {Methenyl - H4MPT + F420H2}}$	methylene-H₄MPT dehydrogenase	${\ce {methylene-H4MPT}}$
5	${\ce {Methylene - H4MPT + F420H2}}$	methylene-H₄MPT reductase	${\ce {methyl-H4MPT}}$
6	${\ce {methyl-H4MPT + HS-CoM}}$	methyl-H₄MPT/HSCoM methyl transferase	${\ce {CH3-S-CoM}}$
7	${\ce {CH3-S-CoM + HS-CoB}}$	methyl-S-CoM reductase	${\ce {CoM-S-S-CoB}}$
8	${\ce {CoM-S-S-CoB + Fdx (ferredoxin)}}$	electron bifurcating hydrogenase-heterodisulfide reductase complex	${\ce {Fdx^2- + HS-CoB + HS-CoM}}$
9	${\ce {F420 + H2 + HCO2H}}$	F₄₂₀-reducing hydrogenase	${\ce {CO2 + F420H}}$
10
11
12

Some of the products formed during step 9 are fed into steps 4 and step 5.

Step 1 - Starts by combing ${\ce {CO2}}$ ${\ce {CO2}}$ , Methanofuran (MFR), and two ${\ce {H+}}$ ${\ce {H+}}$ this reaction produces formyl-MFR.^[5]
- ${\ce {CO2 + MFR + H+ -> Formyl - MFR}}$
Step 2 -
- ${\ce {Formyl - MFR + H4MPT -> Formyl - H4MPT + MFR}}$
Step 3 -
- ${\ce {Formyl - H4MPT + H+ -> Methenyl - H4MPT+ + H2O}}$
Step 4 - Takes place in two steps
- ${\ce {Methenyl - H4MPT + F420H2 -> Methylene - H4MPT + F420 + H+}}$
- ${\ce {Methenyl - H4MPT + H2 -> Methylene - H4MPT + H+}}$
Step 5 -
- ${\ce {Methylene - H4MPT + F420H2 -> CH3H4MPT + F420}}$
Step 6 - ${\ce {CH3 - H4MPT + CoM - SH -> CH3 - S - CoM + H4MPT}}$
Step 7 - ${\ce {CH3 - S - CoM + CoB - SH -> CoM - S - S - CoB + CH4}}$
Step 8 - Also takes place in two steps
- ${\ce {CoM - S - S - CoB + H2 -> CoM - SH + CoB - SH}}$
- ${\ce {CoM - S - S - CoB + 2H+ -> CoM - SH + CoB - SH}}$
Step 9 -
- ${\ce {H2 + F420 -> F420H2 + H+}}$
Step 10 -
- ${\ce {H2 + Fd(ox) -> H+ + Fd(red)}}$
Step 11 - This step is a repeat of step 10
Step 12 -
- ${\ce {CoM - S - S - CoB + MPhH2 -> CoM - SH + CoB - SH + MPh}}$
Step 13 -
- ${\ce {Na+(in) + H+(out) -> Na+(out) + H+(in)}}$
Step 14 -
- ${\ce {F420H2 + MPh -> F420 + MPhH2}}$
- ${\ce {ADP + Pi -> ATP + H2O}}$

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References

^ ^a ^b ^c ^d ^e ^f ^g ^h Thauer, Rudolf K. (2012-09-18). "The Wolfe cycle comes full circle". Proceedings of the National Academy of Sciences. 109 (38): 15084–15085. doi:10.1073/pnas.1213193109. ISSN 0027-8424. PMC 3458314. PMID 22955879.{{cite journal}}: CS1 maint: PMC format (link)
^ 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". ACS Catalysis. 12 (4): 2606–2622. doi:10.1021/acscatal.1c06036. ISSN 2155-5435.
^ Vo, Chi Hung; Goyal, Nishu; Karimi, Iftekhar A; Kraft, Markus (2020-01). "First Observation of an Acetate Switch in a Methanogenic Autotroph ( Methanococcus maripaludis S2)". Microbiology Insights. 13: 117863612094530. doi:10.1177/1178636120945300. ISSN 1178-6361. PMC 7416134. PMID 32843840. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link)
^ 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, vol. 79, Academic Press, pp. 1–23, doi:10.1016/bs.ampbs.2021.07.003, retrieved 2023-11-27
^ Buan, Nicole R. (2018-12-14). "Methanogens: pushing the boundaries of biology". Emerging Topics in Life Sciences. 2 (4): 629–646. doi:10.1042/etls20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.{{cite journal}}: CS1 maint: PMC format (link)

[:1-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h Thauer, Rudolf K. (2012-09-18). "The Wolfe cycle comes full circle". Proceedings of the National Academy of Sciences. 109 (38): 15084–15085. doi:10.1073/pnas.1213193109. ISSN 0027-8424. PMC 3458314. PMID 22955879.{{cite journal}}: CS1 maint: PMC format (link)

[:0-2] 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". ACS Catalysis. 12 (4): 2606–2622. doi:10.1021/acscatal.1c06036. ISSN 2155-5435.

[3] Vo, Chi Hung; Goyal, Nishu; Karimi, Iftekhar A; Kraft, Markus (2020-01). "First Observation of an Acetate Switch in a Methanogenic Autotroph ( Methanococcus maripaludis S2)". Microbiology Insights. 13: 117863612094530. doi:10.1177/1178636120945300. ISSN 1178-6361. PMC 7416134. PMID 32843840. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link)

[4] 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, vol. 79, Academic Press, pp. 1–23, doi:10.1016/bs.ampbs.2021.07.003, retrieved 2023-11-27

[5] Buan, Nicole R. (2018-12-14). "Methanogens: pushing the boundaries of biology". Emerging Topics in Life Sciences. 2 (4): 629–646. doi:10.1042/etls20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.{{cite journal}}: CS1 maint: PMC format (link)

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Wolfe cycle

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Wolfe Cycle

Discovery

Steps:

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Wolfe cycle

Wolfe Cycle

Discovery

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References

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