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Radical enzymes in anaerobes

Lookup NU author(s): Emeritus Professor Bernard Golding


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This review describes enzymes that contain radicals and/or catalyze reactions with radical intermediates. Because radicals irreversibly react with dioxygen, most of these enzymes occur in anaerobic bacteria and archaea. Exceptions are the families of coenzyme B12- and S-adenosylmethionine (SAM)-dependent radical enzymes, of which some members also occur in aerobes. Especially oxygen-sensitive radical enzymes are the glycyl radical enzymes and 2-hydroxyacyl-CoA dehydratases. The latter are activated by an ATP-dependent one-electron transfer and act via a ketyl radical anion mechanism. Related enzymes are the ATP-dependent benzoyl-CoA reductase and the ATP-independent 4-hydroxybenzoyl-CoA reductase. Ketyl radical anions may also be generated by one-electron oxidation as shown by the flavin-adenine-dinucleotide (FAD)- and [4Fe-4S]-containing 4-hydroxybutyryl-CoA dehydratase. Finally, two radical enzymes are discussed, pyruvate:ferredoxin oxidoreductase and methane-forming methyl-CoM reductase, which catalyze their main reaction in two-electron steps, but subsequent electron transfers proceed via radicals. Copyright © 2006 by Annual Reviews. All rights reserved.

Publication metadata

Author(s): Buckel W, Golding BT

Publication type: Review

Publication status: Published

Journal: Annual Review of Microbiology

Year: 2006

Volume: 60

Pages: 27-49

ISSN (print): 0066-4227

ISSN (electronic): 1545-3251


DOI: 10.1146/annurev.micro.60.080805.142216

PubMed id: 16704345