Reaction Mechanism of Cobalt-Substituted Homoprotocatechuate 2,3-Dioxygenase: A QM/MM Study

The reaction mechanisms of cobalt-substituted homoprotocatechuate 2,3-dioxygenase (Co-HPCD) with electron-rich substrate homoprotocatechuate (HPCA) and electron-poor substrate 4-nitrocatechol (4NC) were investigated by quantum mechanical/molecular mechanical (QM/MM) calculations. Our results demonst...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2015-04, Vol.119 (13), p.4608-4616
Main Authors: Cao, Lili, Dong, Geng, Lai, Wenzhen
Format: Article
Language:English
Subjects:
Activation
Barriers
Catechols - chemistry
Cobalt - chemistry
Dioxygenases - chemistry
Electrons
Ground state
Mathematical analysis
Models, Molecular
Oxygen - chemistry
Physical chemistry
Quantum mechanics
Quantum Theory
Reaction mechanisms
Reactive Oxygen Species - chemistry
Spectroscopy
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Summary:The reaction mechanisms of cobalt-substituted homoprotocatechuate 2,3-dioxygenase (Co-HPCD) with electron-rich substrate homoprotocatechuate (HPCA) and electron-poor substrate 4-nitrocatechol (4NC) were investigated by quantum mechanical/molecular mechanical (QM/MM) calculations. Our results demonstrated that the Co-O2 adducts has doublet ground state with a CoIII-O2 •– character when 4NC was used as the substrate, in good agreement with the EPR spectroscopic experiment. The reactive oxygen species is the doublet CoIII-O2 •– for Co-HPCD/4NC and the quartet SQ•↑-CoII-O2 •–↓ species for Co-HPCD/HPCA, indicating that the substrate plays important roles in the dioxygen activation by Co-HPCD. B3LYP was found to overestimate the rate-limiting barriers in Co-HPCD. TPSSh predicts barriers of 21.5 versus 12.0 kcal/mol for Co-HPCD/4NC versus Co-HPCD/HPCA, which is consistent with the fact that the rate of the reaction is decreased when the substrate was changed from HPCA to 4NC.
ISSN:1520-6106
1520-5207
DOI:10.1021/acs.jpcb.5b00613