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A Novel Non‐oxidative [2+2] Cycloaddition of an Endogenous Substrate Catalyzed by Streptomyces coelicolor Cytochrome P450 154A1

Cytochrome P450 (P450) constitutes a superfamily of enzymes containing a prosthetic heme iron. P450s catalyze a great variety of NADPH‐ and O2‐dependent reactions. These processes normally involve the insertion of one oxygen atom from molecular dioxygen into the substrate, often in a stereospecific and regioselective manner. For almost all catalytic activities, P450s must be complemented with their electron donor partner proteins, either NADPH‐cytochrome P450 reductase (for microsomal eukaryotic P450s) or a ferredoxin/ferredoxin reductase system (for most prokaryotic and mitochondrial P450s). Here we report a comprehensive genetic, metabolomic, and biochemical study on Streptomyces coelicolor cytochrome P450 (P450) 154A1, known to have a unique heme orientation in its crystal structure. Deletion of the P450 154A1 gene compromised the long‐term stability of the organism. A novel dipentaenone with a high degree of conjugation was identified as an endogenous substrate of P450 154A1 using a metabolomics approach. The biotransformation of this substrate by P450 154A1 was shown to be an unexpected intramolecular [2+2] cycloaddition to a Paternò–Büchi ‐like product without oxidation/reduction.(Supported in part by USHS grants R01 GM069970, P30 ES000267)