title: Chloroperoxidase-catalyzed epoxidation of cis-β-methylstyrene: distal pocket flexibility tunes catalytic reactivity.
abstract: Chloroperoxidase, the most versatile heme protein, has a hybrid active site pocket that shares structural features with peroxidases and cytochrome P450s. The simulation studies presented here show that the enzyme possesses a remarkable ability to efficiently utilize its hybrid structure, assuming structurally different peroxidase-like and P450-like distal pocket faces and thereby enhancing the inherent catalytic capability of the active center. We find that, during epoxidation of cis-β-methylstyrene (CBMS), the native peroxidase-like aspect of the distal pocket is diminished as the polar Glu183 side chain is displaced away from the active center and the distal pocket takes on a more hydrophobic, P450-like, aspect. The P450-like distal pocket provides a significant enthalpic stabilization of ∼4 kcal/mol of the 14 kcal/mol reaction barrier for gas-phase epoxidation of CMBS by an oxyferryl heme-thiolate species. This stabilization comes from breathing of the distal pocket. As until recently the active site of chloroperoxidase was postulated to be inflexible, these results suggest a new conceptual understanding of the enzyme's versatility: catalytic reactivity is tuned by flexibility of the distal pocket.
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States. omorozov@fiu.edu
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Morozov
authors.forename: David C
authors.initials: DC
authors.lastname: Chatfield
mesh_terms: D055162:Biocatalysis; D020134:Catalytic Domain; D002711:Chloride Peroxidase / Q000737:chemistry* / Q000378:metabolism*; D004795:Enzyme Stability; D004852:Epoxy Compounds / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D018583:Pliability; D011522:Protons; D011789:Quantum Theory; D013237:Stereoisomerism; D013343:Styrenes / Q000737:chemistry*
chemical_list: D004852:Epoxy Compounds; D011522:Protons; D013343:Styrenes; C027142:vinyltoluene; D002711:Chloride Peroxidase