Oxygen-18 Labeling Reveals a Mixed Fe-O Mechanism in the Last Step of Cytochrome P450 51 Sterol 14α-Demethylation.
Angew Chem Int Ed Engl
; 63(9): e202317711, 2024 02 26.
Article
em En
| MEDLINE
| ID: mdl-38206808
ABSTRACT
The 14α-demethylation step is critical in eukaryotic sterol biosynthesis, catalyzed by cytochrome P450 (P450) Family 51 enzymes, for example, with lanosterol in mammals. This conserved three-step reaction terminates in a C-C cleavage step that generates formic acid, the nature of which has been controversial. Proposed mechanisms involve roles of P450 Compound 0 (ferric peroxide anion, FeO2 - ) or Compound I (perferryl oxygen, FeO3+ ) reacting with either the aldehyde or its hydrate, respectively. Analysis of 18 O incorporation into formic acid from 18 O2 provides a means of distinguishing the two mechanisms. Human P450 51A1 incorporated 88 % 18 O (one atom) into formic acid, consistent with a major but not exclusive FeO2 - mechanism. Two P450 51 orthologs from amoeba and yeast showed similar results, while two orthologs from pathogenic trypanosomes showed roughly equal contributions of both mechanisms. An X-ray crystal structure of the human enzyme showed the aldehyde oxygen atom 3.5â
Å away from the heme iron atom. Experiments with human P450 51A1 and H2 18 O yielded primarily one 18 O atom but 14 % of the formic acid product with two 18 O atoms, indicative of a minor contribution of a Compound I mechanism. LC-MS evidence for a Compound 0-derived Baeyer-Villiger reaction product (a 14α-formyl ester) was also found.
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Base de dados:
MEDLINE
Assunto principal:
Isótopos de Oxigênio
/
Esteróis
/
Sistema Enzimático do Citocromo P-450
/
Formiatos
Limite:
Animals
/
Humans
Idioma:
En
Revista:
Angew Chem Int Ed Engl
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Estados Unidos