Cholesterol Hydroperoxides as Substrates for Cholesterol-Metabolizing Cytochrome P450 Enzymes and Alternative Sources of 25-Hydroxycholesterol and other Oxysterols

• Published in: Angewandte Chemie International Edition 2015-09, Vol.54 (38), p.11138-11142
• Main Authors: van Lier, Johan E., Mast, Natalia, Pikuleva, Irina A.
• Format: Article
• Language: English
• Subjects: autooxidation; biocatalysis; Cholesterol - analogs & derivatives; Cholesterol - metabolism; cholesterol hydroperoxides; Cytochrome P-450 Enzyme System - metabolism; cytochrome p450; Hydroxycholesterols - metabolism; metabolism; Sterols - metabolism; Substrate Specificity
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201505002

The interaction of the primary autoxidation products of cholesterol, namely 25‐ and 20ξ‐hydroperoxides, with the four principal cholesterol‐metabolizing cytochrome P450 enzymes is reported. Addition of cholesterol 25‐hydroperoxide to the enzymes CYP27A1 and CYP11A1 induced well‐defined spectral changes while generating 25‐hydroxycholesterol as the major product. The 20ξ‐hydroperoxides induced spectral shifts in CYP27A1 and CYP11A1 but glycol metabolites were detected only with CYP11A1. CYP7A1 and CYP46A1 failed to give metabolites with any of the hydroperoxides. A P450 hydroperoxide‐shunt reaction is proposed, where the hydroperoxides serve as both donor for reduced oxygen and substrate. CYP27A1 was shown to mediate the reduction of cholesterol 25‐hydroperoxide to 25‐hydroxycholesterol, a role of potential significance for cholesterol‐rich tissues with high oxidative stress. CYP27A1 may participate in the removal of harmful autoxidation products in these tissues, while providing a complementary source of 25‐hydroxycholesterol, a modulator of immune cell function and mediator of viral cell entry. The interaction of the cholesterol autoxidation products 25‐ and 20ξ‐hydroperoxides with cytochrome P450 (CYP) enzymes is reported. The addition of the hydroperoxides to CYP11A1 (structure with 20α‐hydroperoxide shown) and CYP27A1 induced well‐defined spectral changes while the 25‐hydroperoxide generated 25‐hydroxycholesterol as the major product. A P450 hydroperoxide‐shunt reaction is proposed, where the hydroperoxides serve as both the donor for reduced oxygen and substrate.