On the stoichiometry of the oxidase and monooxygenase reactions catalyzed by liver microsomal cytochrome P-450. Products of oxygen reduction.
J Biol Chem
; 259(11): 6812-7, 1984 Jun 10.
Article
en En
| MEDLINE
| ID: mdl-6725272
This laboratory has recently reported that, in a reconstituted enzyme system containing alcohol-induced isozyme 3a of liver microsomal cytochrome P-450, the sum of acetaldehyde generated by the monooxygenation of ethanol and of hydrogen peroxide produced by the NADPH oxidase activity is inadequate to account for the O2 and NADPH consumed. Studies on the stoichiometry have revealed the occurrence of an additional reaction involving an overall 4-electron transfer to molecular oxygen which is presumed to yield water: O2 + 2 NADPH + 2H+----2 H2O + 2 NADP+. The occurrence of a peroxidase reaction in which free H2O2 is reduced to water by NADPH was ruled out. When the 4-electron oxidase activity is taken into account, measurements of NADPH oxidation and O2 consumption are in accord with the amounts of products formed in the presence of various P-450 isozymes, either in the absence or presence of typical substrates, including those which undergo hydroxylation, N- or O-demethylation, or oxidation of hydroxymethyl to aldehyde groups. Of the substrates examined, some had no effect on the oxidase reaction yielding hydrogen peroxide or the 4-electron oxidase reaction, some were inhibitory, and some were stimulatory, but the same substrate did not necessarily have the same effect on the two reactions.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Oxidorreductasas
/
Oxigenasas
/
Microsomas Hepáticos
/
Sistema Enzimático del Citocromo P-450
Límite:
Animals
Idioma:
En
Revista:
J Biol Chem
Año:
1984
Tipo del documento:
Article
Pais de publicación:
Estados Unidos