Benutzer:Spargel 24/Coenzyme B
Vorlage:Chembox Coenzyme B is a coenzyme required for redox reactions in methanogens. The full chemical name of coenzyme B is 7-mercaptoheptanoylthreoninephosphate.[1] The molecule contains a thiol, which is its principal site of reaction.
Coenzyme B reacts with 2-methylthioethanesulfonate (methyl-Coenzyme M, abbreviated CH3-S-CoM), to release methane in methanogenesis:[2]
- CH3-S-CoM + HS-CoB → CH4 + CoB-S-S-CoM
This conversion is catalyzed by the enzyme methyl coenzyme M reductase, which contains cofactor F430 as the prosthetic group.
A related conversion that utilizes both HS-CoB and HS-CoM is the reduction of fumarate to succinate, catalyzed by fumarate reductase:[3]
- CH3-S-CoM + HS-CoB -O2CCH=CHCO2- → -O2CCH2-CH2CO2- + CoB-S-S-CoM
References
- ↑ Noll KM, Rinehart KL, Tanner RS, Wolfe RS: Structure of component B (7-mercaptoheptanoylthreonine phosphate) of the methylcoenzyme M methylreductase system of Methanobacterium thermoautotrophicum. In: Proc. Natl. Acad. Sci. U.S.A. 83. Jahrgang, Nr. 12, 1986, S. 4238–42, doi:10.1073/pnas.83.12.4238, PMID 3086878, PMC 323707 (freier Volltext) – (nih.gov).
- ↑ Thauer, R. K., "Biochemistry of Methanogenesis: a Tribute to Marjory Stephenson", Microbiology, 1998, volume 144, pages 2377-2406.
- ↑ Heim, S.; Künkel, A.; Thauer, R. K.; Hedderich, R. “Thiol:fumarate Reductase (Tfr) from Methanobacterium thermoautotrophicum: Identification of the Catalytic Sites for Fumarate Reduction and Thiol Oxidation” European Journal of Biochemistry 1998, volume 253, pages 292-299.