Coenzyme B

Coenzyme B
IUPAC name	2-[(7-mercapto-1-oxoheptyl)amino]-3-phosphonooxybutanoic acid
Identifiers
CAS number	[104302-77-4]
PubChem	350
SMILES	CC(C(C(=O)O)NC(=O)CCCCCCS)OP(=O)(O)O
ChemSpider ID	343
Properties
Molecular formula	C11H22NO7PS
Molar mass	343.333641
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

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

1. ^ Noll KM, Rinehart KL, Tanner RS, Wolfe RS (1986). "Structure of component B (7-mercaptoheptanoylthreonine phosphate) of the methylcoenzyme M methylreductase system of Methanobacterium thermoautotrophicum". Proc. Natl. Acad. Sci. U.S.A. 83 (12): 4238–42. doi:10.1073/pnas.83.12.4238. PMID 3086878. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=3086878. 
2. ^ Thauer, R. K., "Biochemistry of Methanogenesis: a Tribute to Marjory Stephenson", Microbiology, 1998, volume 144, pages 2377-2406.
3. ^ 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.

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