Cytochromes P450 catalyze the reduction of α,β-unsaturated aldehydes

Immaculate Amunom, Laura J. Dieter, V. Tamási, Jian Cai, Daniel J. Conklin, Sanjay Srivastava, Martha V. Martin, F. Peter Guengerich, Russell A. Prough

Research output: Contribution to journalArticle

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Abstract

The metabolism of α,β-unsaturated aldehydes, e.g., 4-hydroxynonenal, involves oxidation to carboxylic acids, reduction to alcohols, and glutathionylation to eventually form mercapturide conjugates. Recently, we demonstrated that P450s can oxidize aldehydes to carboxylic acids, a reaction previously thought to involve aldehyde dehydrogenase. When recombinant cytochrome P450 3A4 was incubated with 4-hydroxynonenal, O 2, and NADPH, several products were produced, including 1,4-dihydroxynonene (DHN), 4-hydroxy-2-nonenoic acid (HNA), and an unknown metabolite. Several P450s catalyzed the reduction reaction in the order (human) P450 2B6 ≅ P450 3A4 > P450 1A2 > P450 2J2 > (mouse) P450 2c29. Other P450s did not catalyze the reduction reaction (human P450 2E1 and rabbit P450 2B4). Metabolism by isolated rat hepatocytes showed that HNA formation was inhibited by cyanamide, while DHN formation was not affected. Troleandomycin increased HNA production 1.6-fold while inhibiting DHN formation, suggesting that P450 3A11 is a major enzyme involved in rat hepatic clearance of 4-HNE. A fluorescent assay was developed using 9-anthracenealdehyde to measure both reactions. Feeding mice a diet containing t-butylated hydroxyanisole increased the level of both activities with hepatic microsomal fractions but not proportionally. Miconazole (0.5 mM) was a potent inhibitor of these microsomal reduction reactions, while phenytoin and α-naphthoflavone (both at 0.5 mM) were partial inhibitors, suggesting the role of multiple P450 enzymes. The oxidative metabolism of these aldehydes was inhibited >90% in an Ar or CO atmosphere, while the reductive reactions were not greatly affected. These results suggest that P450s are significant catalysts of the reduction of α,β-unsaturated aldehydes in the liver.

Original languageEnglish
Pages (from-to)1223-1230
Number of pages8
JournalChemical Research in Toxicology
Volume24
Issue number8
DOIs
Publication statusPublished - Aug 15 2011

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Aldehydes
Cytochrome P-450 Enzyme System
Metabolism
Carboxylic Acids
Liver
Cyanamide
Troleandomycin
Rats
Butylated Hydroxyanisole
Miconazole
Cytochrome P-450 CYP3A
Aldehyde Dehydrogenase
Acids
Phenytoin
Carbon Monoxide
Atmosphere
NADP
Hepatocytes
Nutrition
Metabolites

ASJC Scopus subject areas

  • Toxicology

Cite this

Amunom, I., Dieter, L. J., Tamási, V., Cai, J., Conklin, D. J., Srivastava, S., ... Prough, R. A. (2011). Cytochromes P450 catalyze the reduction of α,β-unsaturated aldehydes. Chemical Research in Toxicology, 24(8), 1223-1230. https://doi.org/10.1021/tx200080b

Cytochromes P450 catalyze the reduction of α,β-unsaturated aldehydes. / Amunom, Immaculate; Dieter, Laura J.; Tamási, V.; Cai, Jian; Conklin, Daniel J.; Srivastava, Sanjay; Martin, Martha V.; Guengerich, F. Peter; Prough, Russell A.

In: Chemical Research in Toxicology, Vol. 24, No. 8, 15.08.2011, p. 1223-1230.

Research output: Contribution to journalArticle

Amunom, I, Dieter, LJ, Tamási, V, Cai, J, Conklin, DJ, Srivastava, S, Martin, MV, Guengerich, FP & Prough, RA 2011, 'Cytochromes P450 catalyze the reduction of α,β-unsaturated aldehydes', Chemical Research in Toxicology, vol. 24, no. 8, pp. 1223-1230. https://doi.org/10.1021/tx200080b
Amunom, Immaculate ; Dieter, Laura J. ; Tamási, V. ; Cai, Jian ; Conklin, Daniel J. ; Srivastava, Sanjay ; Martin, Martha V. ; Guengerich, F. Peter ; Prough, Russell A. / Cytochromes P450 catalyze the reduction of α,β-unsaturated aldehydes. In: Chemical Research in Toxicology. 2011 ; Vol. 24, No. 8. pp. 1223-1230.
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AU - Amunom, Immaculate

AU - Dieter, Laura J.

AU - Tamási, V.

AU - Cai, Jian

AU - Conklin, Daniel J.

AU - Srivastava, Sanjay

AU - Martin, Martha V.

AU - Guengerich, F. Peter

AU - Prough, Russell A.

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N2 - The metabolism of α,β-unsaturated aldehydes, e.g., 4-hydroxynonenal, involves oxidation to carboxylic acids, reduction to alcohols, and glutathionylation to eventually form mercapturide conjugates. Recently, we demonstrated that P450s can oxidize aldehydes to carboxylic acids, a reaction previously thought to involve aldehyde dehydrogenase. When recombinant cytochrome P450 3A4 was incubated with 4-hydroxynonenal, O 2, and NADPH, several products were produced, including 1,4-dihydroxynonene (DHN), 4-hydroxy-2-nonenoic acid (HNA), and an unknown metabolite. Several P450s catalyzed the reduction reaction in the order (human) P450 2B6 ≅ P450 3A4 > P450 1A2 > P450 2J2 > (mouse) P450 2c29. Other P450s did not catalyze the reduction reaction (human P450 2E1 and rabbit P450 2B4). Metabolism by isolated rat hepatocytes showed that HNA formation was inhibited by cyanamide, while DHN formation was not affected. Troleandomycin increased HNA production 1.6-fold while inhibiting DHN formation, suggesting that P450 3A11 is a major enzyme involved in rat hepatic clearance of 4-HNE. A fluorescent assay was developed using 9-anthracenealdehyde to measure both reactions. Feeding mice a diet containing t-butylated hydroxyanisole increased the level of both activities with hepatic microsomal fractions but not proportionally. Miconazole (0.5 mM) was a potent inhibitor of these microsomal reduction reactions, while phenytoin and α-naphthoflavone (both at 0.5 mM) were partial inhibitors, suggesting the role of multiple P450 enzymes. The oxidative metabolism of these aldehydes was inhibited >90% in an Ar or CO atmosphere, while the reductive reactions were not greatly affected. These results suggest that P450s are significant catalysts of the reduction of α,β-unsaturated aldehydes in the liver.

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