title: Active species of horseradish peroxidase (HRP) and cytochrome P450: two electronic chameleons.
abstract: The active site of HRP Compound I (Cpd I) is modeled using hybrid density functional theory (UB3LYP). The effects of neighboring amino acids and of environmental polarity are included. The low-lying states have porphyrin radical cationic species (Por(*)(+)). However, since the Por(*)(+) species is a very good electron acceptor, other species, which can be either the ligand or side chain amino acid residues, may participate in electron donation to the Por(*)(+) moiety, thereby making Cpd I behave like a chemical chameleon. Thus, this behavior that was noted before for Cpd I of P450 is apparently much more wide ranging than initially appreciated. Since chemical chameleonic behavior property was found to be expressed not only in the properties of Cpd I itself, but also in its reactivity, the roots of this phenomenon are generalized. A comparative discussion of Cpd I species follows for the enzymes HRP, CcP, APX, CAT (catalase), and P450.
authors.affiliation: Department of Organic Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Sam P
authors.initials: SP
authors.lastname: de Visser
authors.forename: Sason
authors.initials: S
authors.lastname: Shaik
authors.forename: Pankaz K
authors.initials: PK
authors.lastname: Sharma
authors.forename: Devesh
authors.initials: D
authors.lastname: Kumar
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
mesh_terms: D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D013816:Thermodynamics
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006735:Horseradish Peroxidase