Coenzyme-B sulfoethylthiotransferase explained

coenzyme-B sulfoethylthiotransferase
Ec Number:	2.8.4.1
Go Code:	0044674

In enzymology, coenzyme-B sulfoethylthiotransferase, also known as methyl-coenzyme M reductase (MCR) or most systematically as 2-(methylthio)ethanesulfonate:N-(7-thioheptanoyl)-3-O-phosphothreonine S-(2-sulfoethyl)thiotransferase is an enzyme that catalyzes the final step in the formation of methane.^[1] It does so by combining the hydrogen donor coenzyme B and the methyl donor coenzyme M. Via this enzyme, most of the natural gas on earth was produced. Ruminants (e.g. cows) produce methane because their rumens contain methanogenic prokaryotes (Archaea)^{[2] [3]} that encode and express the set of genes of this enzymatic complex.

The enzyme has two active sites, each occupied by the nickel-containing F₄₃₀ cofactor.^[4]

+ CoM-S-S-CoB + methane

The two substrates of this enzyme are 2-(methylthio)ethanesulfonate and N-(7-mercaptoheptanoyl)threonine 3-O-phosphate; its two products are CoM-S-S-CoB and methane. 3-Nitrooxypropanol inhibits the enzyme.^[5]

In some species, the enzyme reacts in reverse (a process called reverse methanogenesis), catalysing the anaerobic oxidation of methane, therefore removing it from the environment.^[6] Such organisms are methanotrophs.

This enzyme belongs to the family of transferases, specifically those transferring alkylthio groups.

This enzyme participates in folate biosynthesis.

Structure

Coenzyme-B sulfoethylthiotransferase is a multiprotein complex made up of a pair of identical halves. Each half is made up of three subunits: α, β and γ,^[7] also called McrA, McrB and McrG, respectively.

Further reading

• Bobik TA, Olson KD, Noll KM, Wolfe RS . Evidence that the heterodisulfide of coenzyme M and 7-mercaptoheptanoylthreonine phosphate is a product of the methylreductase reaction in Methanobacterium . Biochemical and Biophysical Research Communications . 149 . 2 . 455–60 . December 1987 . 3122735 . 10.1016/0006-291X(87)90389-5 .
• Ellermann J, Rospert S, Thauer RK, Bokranz M, Klein A, Voges M, Berkessel A . Methyl-coenzyme-M reductase from Methanobacterium thermoautotrophicum (strain Marburg). Purity, activity and novel inhibitors . European Journal of Biochemistry . 184 . 1 . 63–8 . September 1989 . 2506016 . 10.1111/j.1432-1033.1989.tb14990.x . free .
• Signor L, Knuppe C, Hug R, Schweizer B, Pfaltz A, Jaun B . Methane formation by reaction of a methyl thioether with a photo-excited nickel thiolate--a process mimicking methanogenesis in archaea . Chemistry: A European Journal . 6 . 19 . 3508–16 . October 2000 . 11072815 . 10.1002/1521-3765(20001002)6:19<3508::AID-CHEM3508>3.0.CO;2-W .

Notes and References

1. Book: Ragdale . Stephen W. . Peter M.H. Kroneck and Martha E. Sosa Torres . The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment . Metal Ions in Life Sciences . 14 . 2014 . Springer . Chapter 6. Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis and the First Step in Anaerobic Oxidation of the Greenhouse Gas Methane . 125–145 . 10.1007/978-94-017-9269-1_6 . 25416393 .
2. Web site: Bovine Rumen - microbewiki.
3. Whitford MF, Teather RM, Forster RJ . Phylogenetic analysis of methanogens from the bovine rumen . BMC Microbiology . 1 . 5 . 2001 . 11384509 . 32158 . 10.1186/1471-2180-1-5 . free .
4. Thauer RK . Biochemistry of methanogenesis: a tribute to Marjory Stephenson. 1998 Marjory Stephenson Prize Lecture . Microbiology . 144 . 9. 2377–406 . September 1998 . 9782487 . 10.1099/00221287-144-9-2377 . free .
5. Hristov AN, Oh J, Giallongo F, Frederick TW, Harper MT, Weeks HL, Branco AF, Moate PJ, Deighton MH, Williams SR, Kindermann M, Duval S . An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production . Proceedings of the National Academy of Sciences of the United States of America . 112 . 34 . 10663–8 . August 2015 . 26229078 . 4553761 . 10.1073/pnas.1504124112 . 2015PNAS..11210663H . free .
6. Hallam SJ, Putnam N, Preston CM, Detter JC, Rokhsar D, Richardson PM, DeLong EF . Reverse methanogenesis: testing the hypothesis with environmental genomics . Science . 305 . 5689 . 1457–62 . September 2004 . 15353801 . 10.1126/science.1100025 . 2004Sci...305.1457H . 31107045 .
7. Ermler U, Grabarse W, Shima S, Goubeaud M, Thauer RK . Crystal structure of methyl-coenzyme M reductase: the key enzyme of biological methane formation . Science . 278 . 5342 . 1457–62 . November 1997 . 9367957 . 10.1126/science.278.5342.1457 . 1997Sci...278.1457E .