Activation of triplet dioxygen by glucose oxidase: Spin-orbit coupling in the superoxide ion
2002 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 106, no 14, 3742-3750 p.Article in journal (Refereed) Published
Hybrid density functional calculations have been performed for the reductive activation of dioxygen by glucose oxidase, for which recent experiments have shown substantial kinetic O-18 isotope effects but no deuterium isotope effect, The present analysis of the mechanism suggests that this surprising isotope effect is best explained if the rate-determining step is the triplet --> singlet interconversion that follows after the electron transfer and the superoxide ion production. The oxygen isotope effect is rationalized by an analysis of the spin-orbit coupling in the radical pair M.+..O-2(.-), where M is the FADH(2) cofactor. For the electron transfer between the M and O-2, the presence of the protonated His516 plays a crucial role by strongly increasing the electron affinity Of O-2, which makes the electron transfer exothermic and allows it to occur without any barrier. The chemical step where hydrogen peroxide is formed has a computed free-energy barrier of only 6.6 kcal/mol.
Place, publisher, year, edition, pages
2002. Vol. 106, no 14, 3742-3750 p.
photosynthetic algae, aspergillus-niger, molecular-oxygen, biochemistry, transitions, energies, behavior, spectra, model, state
IdentifiersURN: urn:nbn:se:kth:diva-21470DOI: 10.1021/jp014013qISI: 000175022100032OAI: oai:DiVA.org:kth-21470DiVA: diva2:340168
QC 201005252010-08-102010-08-10Bibliographically approved