To elucidate the structural basis for the broad spectrum of activity and the mechanism of CPO-catalyzed enantioselective epoxidation of selected olefin, the structures of the CPO and its olefin complex were studied by both X-ray crystal crystallographic and computational techniques using recombinant CPO expressed in <i>A. niger</i>. Our results revealed that despite functional similarities with wild type CPO, recombinant CPO is over glycosylated with more mannose. Furthermore, a slight difference in the distal pocket is noted, although the active site heme coordination and the overall tertiary structure of the recombinant and wild type CPO are essentially identical. The functional hybrid of a heme peroxidase-cytochrome P450 in CPO accounts for the protein’s broad spectrum of activity.  Molecular docking studies demonstrated the roles of Phe 103 and Phe 186 in CPO catalyzed enantioselective epoxidations of ethyl 3-methylbut-3-enoate, an olefin involved in the synthesis of (R)-(-)-mevalonic acid for the understanding of biosynthetic pathways of sterols, terpenes, and corotenoids. It is observed that ethyl 3-methylbut-3-enoate forms a complex with CPO at a relatively flexible channel through hydrogen bond interactions with Ala 75 coupled with other Pi-interactions between Phe 186 and the carbon-carbon double bond of the substrate, ensuring its enantioselective transformation.

Crystal structure of recombinant chloroperoxidase and molecular docking studies of chloroperoxidase-substrate complex: Insights into the mechanism of chloroperoxidase-catalyzed enantioselective epoxidation of Olefin

ACS Fall 2021

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