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- Title
Interpretation of the reactivity of peroxidase compound II with phenols and anilines using the Marcus equation.
- Authors
Fenoll, Lorena G.; García-Molina, Francisco; Gilabert, María A.; Varó n, Ramón; García-Ruiz, Pedro A.; Tudela, José; García-Cánovas, Francisco; Rodríguez-López, José N.
- Abstract
The catalytic cycle of heme peroxidases involves three processes: the formation of compound I, its conversion to compound II and regeneration of the native enzyme. Each of the processes consists of a reversible binding stage followed by an irreversible transformation stage. Our group has proposed a continuous, sensitive and reliable chronometric method for measuring the steady-state rate of peroxidase activity. Furthermore, we have derived an analytical expression for the steady-state rate and simplified it, taking into consideration the experimental values of the rate constants of some stages previously determined by other authors in stopped-flow assays. We determined the value of the constant for the transformation of a series of phenols and anilines by compound II, and found that it involves a deprotonation step and an electron transfer step. Study of the solvent deuterium isotope effect on the oxidation of phenol revealed the non-rate-limiting character of the deprotonation step in a proton inventory study. Usage of the Marcus equation showed that the electronic transfer step is rate-limiting in both cases, while phenols and anilines were oxidised at different rates for the same potentials. This can be attributed to the shorter electron-tunnelling distance for electron transfer to the iron ion in the phenols than in the anilines.
- Subjects
ANILINE; VITAMIN C; PEROXIDASE; PHENOLS; REACTION mechanisms (Chemistry)
- Publication
Biological Chemistry, 2005, Vol 386, Issue 4, p351
- ISSN
1431-6730
- Publication type
Article
- DOI
10.1515/BC.2005.042