Coenzyme M is a

coenzyme A cofactor is a non-protein chemical compound or Metal ions in aqueous solution, metallic ion that is required for an enzyme's role as a catalysis, catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can ...

required for methyl-transfer reactions in the

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...

methanogen Methanogens are anaerobic archaea that produce methane as a byproduct of their energy metabolism, i.e., catabolism. Methane production, or methanogenesis, is the only biochemical pathway for Adenosine triphosphate, ATP generation in methanogens. A ...

s, and in the metabolism of other substrates in

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. It is also a necessary cofactor in the metabolic pathway of alkene-oxidizing bacteria. CoM helps eliminate the toxic epoxides formed from the oxidation of alkenes such as propylene. The structure of this coenzyme was discovered by CD Taylor and RS Wolfe in 1974 while they were studying methanogenesis, the process by which carbon dioxide is transformed into methane in some archaea. The coenzyme is an

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

with the formula . It is named 2-mercaptoethanesulfonate and abbreviated HS–CoM. The

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

is unimportant, but the sodium salt is most available. Mercaptoethanesulfonate contains both a

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

, which is the main site of reactivity, and a

sulfonate In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the conjugate bases of ...

group, which confers solubility in aqueous media.

Biochemical role

Methanogenesis

The coenzyme is the C1 donor in

methanogenesis Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. It is the fourth and final stage of anaerobic digestion. Organisms capable of producing methane for energy conservation h ...

. It is converted to methyl-coenzyme M thioether, the

thioether In organic chemistry, a sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity as shown on right. Like many other sulfur-containing compounds, Volatile organic compound, volatile sulfides have ...

, in the penultimate step to

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

formation. Methyl-coenzyme M reacts with

coenzyme B Coenzyme B is a coenzyme required for redox reactions in methanogens. The full chemical name of coenzyme B is 7-mercaptoheptanoylthreoninephosphate. The molecule contains a thiol, which is its principal site of reaction. Coenzyme B reacts with 2- ...

, 7-thioheptanoylthreoninephosphate, to give a heterodisulfide, releasing methane: : CH₃–S–CoM + HS–CoB → CH₄ + CoB–S–S–CoM This induction is catalyzed by the

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

methyl-coenzyme M reductase, which restricts cofactor F430 as the

prosthetic group A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein. Not to be confused with the cosubstrate that binds to the enzyme apoenzyme (e ...

. CH₃-S-CoM is produced by the ''MtaA''-catalyzed reaction between a methylated version of monomethylamine corrinoid protein ''MtmC'' and HS-CoM. The methylated version of ''MtmC'' is in turn produced by a cobamide-dependent methyltransferase that uses trimethylamine (TMA), dimethylamine (DMA), or monomethylamine (MMA) as the mehyl donor.

Alkene metabolism

Coenzyme M is also used to make acetoacetate from CO₂ and propylene or ethylene in aerobic bacteria. Specifically, in bacteria that oxidize alkenes into epoxides. After the propylene (or other alkene) undergoes epoxidation and becomes epoxypropane it becomes electrophilic and toxic. These epoxides react with DNA and proteins, affecting cell function. Alkene-oxidizing bacteria like '' Xanthobacter autotrophicus'' use a metabolic pathway in which CoM is conjugated with an aliphatic epoxide. This step creates a nucleophilic compound which can react with CO₂. The eventual carboxylation produces acetoacetate, breaking down the propylene.

Biosynthesis

Bacteria and archaea use different synthetic routes, albeit both starting with

phosphoenolpyruvate Phosphoenolpyruvate (2-phosphoenolpyruvate, PEP) is the carboxylic acid derived from the enol of pyruvate and a phosphate anion. It exists as an anion. PEP is an important intermediate in biochemistry. It has the high-energy phosphate, highest-e ...

References

{{Enzyme cofactors Coenzymes Thiols Sulfonates

Biochemical role

Methanogenesis

Alkene metabolism

Biosynthesis

See also

References