Coenzyme M

Coenzyme M

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Coenzyme M is a coenzyme required for methyl-transfer reactions in the metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 of methanogen
Methanogen
Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are classified as archaea, a group quite distinct from bacteria...

s. The coenzyme is an anion with the formula . It is named 2-mercaptoethanesulfonate and abbreviated HS–CoM. The cation is unimportant, but the sodium salt
Mesna
Mesna is an organosulfur compound. It is used in cancer chemotherapy involving cyclophosphamide and ifosfamide as an adjuvant. It is marketed by Baxter as Uromitexan and Mesnex...

 is most available. Mercaptoethanesulfonate contains both a thiol
Thiol
In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...

, which is the main site of reactivity, and a sulfonate
Sulfonate
A sulfonate is a salt or ester of a sulfonic acid. It contains the functional group R-SO2O-.- Sulfonate salts:Anions with the general formula RSO2O− are called sulfonates. They are the conjugate bases of sulfonic acids with formula RSO2OH. As sulfonic acids tend to be strong acids, the...

 group, which confers solubility in aqueous media.

Biochemical role


The coenzyme is the C1 carrier in methanogenesis
Methanogenesis
Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. Organisms capable of producing methane have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with...

. It is converted to methyl coenzyme M, the thioether
Thioether
A thioether is a functional group in organosulfur chemistry with the connectivity C-S-C as shown on right. Like many other sulfur-containing compounds, volatile thioethers have foul odors. A thioether is similar to an ether except that it contains a sulfur atom in place of the oxygen...

 , in the penultimate step to methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 formation. Coenzyme M reacts with coenzyme B
Coenzyme B
Coenzyme B is a coenzyme required for redox reactions in methanogens. The full chemical name of coenzyme B is 7-mercaptoheptanoylthreoninephosphate...

, 7-thioheptanoylthreoninephosphate, to give a heterodisulfide, releasing methane:
+ HS–CoB → + CoB–S–S–CoM

This conversion is catalyzed by the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 methyl coenzyme M reductase, which contains cofactor F430
Cofactor F430
F430 is the prosthetic group of the enzyme methyl coenzyme M reductase. It is found only in methanogenic Archaea. This enzyme catalyzes the release of methane in the final step of methanogenesis:-Corphin in context:...

 as the prosthetic group.