title: Electronic state of the molecular oxygen released by catalase.
abstract: In catalases, the high redox intermediate known as compound I (Cpd I) is reduced back to the resting state by means of hydrogen peroxide in a 2-electron reaction [Cpd I (Por(*+)-Fe(IV)O) + H(2)O(2) --> Enz (Por-Fe(III)) + H(2)O + O(2)]. It has been proposed that this reaction takes place via proton transfer toward the distal His and hydride transfer toward the oxoferryl oxygen (H(+)/H(-) scheme) and some authors have related it to singlet oxygen generation. Here, we consider the possible reaction schemes and qualitatively analyze the electronic state of the species involved to show that the commonly used association of the H(+)/H(-) scheme with singlet oxygen production is not justified. The analysis is complemented with density functional theory (DFT) calculations for a gas-phase active site model of the reactants and products.
authors.affiliation: Laboratori de Simulació Computacional i Modelització (CoSMoLab), Parc Científic de Barcelona, Baldiri Reixac 10-12, 08028 Barcelona, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Alfonso-Prieto
authors.forename: Pietro
authors.initials: P
authors.lastname: Vidossich
authors.forename: Antonio
authors.initials: A
authors.lastname: Rodríguez-Fortea
authors.forename: Xavi
authors.initials: X
authors.lastname: Carpena
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fita
authors.forename: Peter C
authors.initials: PC
authors.lastname: Loewen
authors.forename: Carme
authors.initials: C
authors.lastname: Rovira
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002374:Catalase / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D004581:Electronics; D004583:Electrons; D006418:Heme / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D008837:Micrococcus / Q000201:enzymology; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D011487:Protein Conformation; D011522:Protons; D026082:Singlet Oxygen / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011522:Protons; D014867:Water; D026082:Singlet Oxygen; D006418:Heme; D006861:Hydrogen Peroxide; D002374:Catalase; D010100:Oxygen