Volume 24, Issue 20 p. 5388-5395
Full Paper

Theory Uncovers the Role of the Methionine–Tyrosine–Tryptophan Radical Adduct in the Catalase Reaction of KatGs: O2 Release Mediated by Proton-Coupled Electron Transfer

Dr. Binju Wang

Dr. Binju Wang

Departament de Química Inorgànica i Orgànica, (secció de Química Orgànica) &, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain

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Prof. Dr. Ignacio Fita

Prof. Dr. Ignacio Fita

Instituto de Biología Molecular (IBMB-CSIC) and, Maria de Maeztu Unit of Excellence. Barcelona Science Park, Baldiri i Reixac 10., 08028 Barcelona, Spain

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Prof. Dr. Carme Rovira

Corresponding Author

Prof. Dr. Carme Rovira

Departament de Química Inorgànica i Orgànica, (secció de Química Orgànica) &, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain

Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain

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First published: 20 February 2018
Citations: 4

Graphical Abstract

QM/MM calculations and QM/MM metadynamics simulations have uncovered the precise catalytic role of the M-Y-W cation radical adduct in the catalase reaction of KatGs. Our results demonstrate that O2 formation proceeds through a mechanism involving proton-coupled electron transfer, which is mediated by the M-Y-W cation radical adduct.

Abstract

Catalase–peroxidases (KatGs) are bifunctional enzymes exhibiting both peroxidase and substantial catalase activities. It is widely recognized from experiments that the catalatic activity of KatGs is correlated with a unique covalent adduct (M-Y-W) formed in the active site, but the exact role of this adduct was elusive up to now. Here, quantum mechanical/molecular mechanical (QM/MM) calculations and QM/MM metadynamics are employed to elucidate the molecular mechanism and the role of M-Y-W adduct in the catalase reaction. It is shown that O2 formation proceeds through a mechanism involving proton-coupled electron transfer (PCET). The M-Y-W cation radical adduct, which is close to the heme, His112 and the HOO. radical intermediate, acts as an electron sink during the PCET process. The present study also highlights the structural differences and functional similarities between KatGs and monofunctional catalases.

Conflict of interest

The authors declare no conflict of interest.