Publications

• Aliphatic epoxide carboxylation.

  Ensign S.A., Allen J.R.

  Aliphatic epoxides (epoxyalkanes) are highly reactive electrophilic molecules that are formed from the monooxygenase-catalyzed epoxidation of aliphatic alkenes. The bacterial metabolism of short-chain epoxyalkanes occurs by a three-step pathway resulting in net carboxylation to beta-ketoacids. Thi ... >> More

  Aliphatic epoxides (epoxyalkanes) are highly reactive electrophilic molecules that are formed from the monooxygenase-catalyzed epoxidation of aliphatic alkenes. The bacterial metabolism of short-chain epoxyalkanes occurs by a three-step pathway resulting in net carboxylation to beta-ketoacids. This pathway uses the atypical cofactor coenzyme M (CoM; 2-mercaptoethanesulfonic acid) as the nucleophile for the epoxide ring opening and as the carrier of 2-hydroxyalkyl- and 2-ketoalkyl-CoM intermediates. Four enzymes are involved in epoxide carboxylation: a zinc-dependent alkyltransferase, two short-chain dehydrogenases with specificities for the chiral products of the R- and S-1,2-epoxyalkane ring opening, and an NADPH:disulfide oxidoreductase/carboxylase that reduces the thioether bond of the 2-ketoalkyl-CoM conjugate and carboxylates the resulting carbanion. In this review, we summarize the biochemical, mechanistic, and structural features of the enzymes of epoxide carboxylation and show how these enzymes, together with CoM, work in concert to achieve this highly unusual carboxylation reaction. << Less

  Annu. Rev. Biochem. 72:55-76(2003) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• A role for coenzyme M (2-mercaptoethanesulfonic acid) in a bacterial pathway of aliphatic epoxide carboxylation.

  Allen J.R., Clark D.D., Krum J.G., Ensign S.A.

  The bacterial metabolism of short-chain aliphatic alkenes occurs via oxidation to epoxyalkanes followed by carboxylation to beta-ketoacids. Epoxyalkane carboxylation requires four enzymes (components I-IV), NADPH, NAD(+), and a previously unidentified nucleophilic thiol. In the present work, coenz ... >> More

  The bacterial metabolism of short-chain aliphatic alkenes occurs via oxidation to epoxyalkanes followed by carboxylation to beta-ketoacids. Epoxyalkane carboxylation requires four enzymes (components I-IV), NADPH, NAD(+), and a previously unidentified nucleophilic thiol. In the present work, coenzyme M (2-mercaptoethanesulfonic acid), a compound previously found only in the methanogenic Archaea where it serves as a methyl group carrier and activator, has been identified as the thiol and central cofactor of aliphatic epoxide carboxylation in the Gram-negative bacterium Xanthobacter strain Py2. Component I catalyzed the addition of coenzyme M to epoxypropane to form a beta-hydroxythioether, 2-(2-hydroxypropylthio)ethanesulfonate. Components III and IV catalyzed the NAD(+)-dependent stereoselective dehydrogenation of R- and S-enantiomers of 2-(2-hydroxypropylthio)ethanesulfonate to form 2-(2-ketopropylthio)ethanesulfonate. Component II catalyzed the NADPH-dependent cleavage and carboxylation of the beta-ketothioether to form acetoacetate and coenzyme M. These findings evince a newfound versatility for coenzyme M as a carrier and activator of alkyl groups longer in chain-length than methane, a function for coenzyme M in a catabolic pathway of hydrocarbon oxidation, and the presence of coenzyme M in the bacterial domain of the phylogenetic tree. These results serve to unify bacterial and Archaeal metabolism further and showcase diverse biological functions for an elegantly simple organic molecule. << Less

  Proc. Natl. Acad. Sci. U.S.A. 96:8432-8437(1999) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.