Enantiospecificity of Chloroperoxidase-Catalyzed Epoxidation: Biased Molecular Dynamics Study of a Cis-β-Methylstyrene/Chloroperoxidase-Compound I Complex

Abstract

Molecular dynamics simulations of an explicitly solvated cis-β-methylstyrene/chloroperoxidase-Compound I complex are performed to determine the cause of the high enantiospecificity of epoxidation. From the simulations, a two-dimensional free energy potential is calculated to distinguish binding potential wells from which reaction to 1S2R and 1R2S epoxide products may occur. Convergence of the free energy potential is accelerated with an adaptive biasing potential. Analysis of binding is followed by analysis of 1S2R and 1R2S reaction precursor structures in which the substrate, having left the binding wells, places its reactive double bond in steric proximity to the oxyferryl heme center. Structural analysis of binding and reaction precursor conformations is presented. We find that 1), a distortion of Glu(183) is important for CPO-catalyzed epoxidation as was postulated previously based on experimental results; 2), the free energy of binding does not provide significant differentiation between structures leading to the respective epoxide enantiomers; and 3), CPO's enantiospecificity toward cis-β-methylstyrene is likely to be caused by a specific group of residues which form a hydrophobic core surrounding the oxyferryl heme center.

Chloroperoxidase-Catalyzed Epoxidation ofcis-β-Methylstyrene: Distal Pocket Flexibility Tunes Catalytic Reactivity

“…In addition to His105 and Glu183, the distal pocket contains a set of hydrophobic residues surrounding the active center. 11,23 This hydrophobic core of residues constitutes most of the steric environment of the active center and is probably the primary cause of the stereoselectivity of oxidations carried out by CPO. 11,22,23 …”

“…Elucidating the nature of this influence is expected to yield understanding of CPO’s catalytic versatility 11,14,22 and of the enantiospecificity of the epoxidation reaction. 11,22,23 The ability of CPO to catalyze many P450-type reactions 7 implies that such a result could also further our understanding of the catalytic functions of P450s, which participate in key biochemical processes in many living species. 41 …”

Nuclear Magnetic Resonance Spectroscopic and Computational Investigations of Chloroperoxidase Catalyzed Regio- and Enantio-Selective Transformations

“…contribute -6.6 to -9.4 kJ/mol per residue to the formation of CPO-indole complex (see Table 2.4). This agrees with reports that these hydrophobic residues interact significantly with hydrophobic substrates such as cis-β-methylstyrene [107,108] and anthracene [176].…”

“…Although the use of computational method for the study of CPO is limited at status quo, this computational method is promising because of the rapid-growing computer technology. Recently, Morozov et al proposed that the simple steric considerations from the hydrophobic core (residues Phe 103, Ile 179, Val 182, and Phe 186) around the oxyferryl heme center govern the stereoselectivity of CPO [107,108], based on the molecular model of cis-β-methylstyrene, a substrate can be oxidized enantioselectively by CPO and H 2 O 2 .…”

“…In 1998, Sundaramoorthy, et al first used computer simulations to address which factors give rise to the pronounced enantioselectivity in epoxidation reactions [27] and suggested that the high enantioselective product is related to favorable interactions between the substrates and Glu 183. Futhermore, according to molecular dynamic simulations of CPO-cis-β-methylstyrene complex, Morozov, et al proposed that enantiomer is likely due to a subtle balance of steric interactions caused by residues Phe 103, Ile 179, Val 182, and Phe 186 around the oxyferyl heme center [107,108].…”