Chloroperoxidase-catalyzed epoxidation of cis-β-methylstyrene: distal pocket flexibility tunes catalytic reactivity

J Phys Chem B. 2012 Nov 1;116(43):12905-14. doi: 10.1021/jp302763h. Epub 2012 Oct 19.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Biocatalysis*
  • Catalytic Domain*
  • Chloride Peroxidase / chemistry*
  • Chloride Peroxidase / metabolism*
  • Enzyme Stability
  • Epoxy Compounds / chemistry*
  • Hydrophobic and Hydrophilic Interactions
  • Molecular Dynamics Simulation*
  • Pliability
  • Protons
  • Quantum Theory
  • Stereoisomerism
  • Styrenes / chemistry*


  • Epoxy Compounds
  • Protons
  • Styrenes
  • vinyltoluene
  • Chloride Peroxidase