Evaluation of norcarane as a probe for radicals in cytochome p450- and soluble methane monooxygenase-catalyzed hydroxylation reactions.
J Am Chem Soc
; 124(24): 6879-86, 2002 Jun 19.
Article
em En
| MEDLINE
| ID: mdl-12059209
ABSTRACT
Norcarane was employed as a mechanistic probe in oxidations catalyzed by hepatic cytochome P450 enzymes and by the soluble methane monooxygenase (sMMO) enzyme from Methylococcuscapsulatus (Bath). In all cases, the major oxidation products (>75%) were endo- and exo-2-norcaranol. Small amounts of 3-norcaranols, 2-norcaranone, and 3-norcaranone also formed. In addition, the rearrangement products (2-cyclohexenyl)methanol and 3-cycloheptenol were detected in the reactions, the former possibly arising from a radical intermediate and the latter ascribed to a cationic intermediate. The formation of the cation-derived rearrangement product is consistent with one or more reaction pathways and is in accord with the results of previous probe studies with the same enzymes. The appearance of the putative radical-derived rearrangement product is in conflict with other mechanistic probe results with the same enzymes. The unique implication of a discrete radical intermediate in hydroxylations of norcarane may be the consequence of a minor reaction pathway for the enzymes that is not manifest in reactions with other probes. Alternatively, it might reflect a previously unappreciated reactivity of norcaranyl cationic intermediates, which can convert to (2-cyclohexenyl)methanol. We conclude that generalizations regarding the intermediacy of radicals in P450 and sMMO enzyme-catalyzed hydroxylations based on the norcarane results should be considered hypothetical until the origin of the unanticipated results can be determined.
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Base de dados:
MEDLINE
Assunto principal:
Oxigenases
/
Terpenos
/
Sistema Enzimático do Citocromo P-450
Limite:
Animals
Idioma:
En
Ano de publicação:
2002
Tipo de documento:
Article