Interpretation of the reactivity of peroxidase compounds I and II with phenols by the Marcus equation

FEBS Letters

Folkes, Lisa K¹  Candeias, Luis P¹ 

[1] Gray Laboratory Cancer Research Trust, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, UK

关键词: Heme peroxidase;    Electron-transfer;    Marcus equation;    Phenoxyl radical;    Stopped-flow;   

DOI  :  10.1016/S0014-5793(97)00792-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The catalytic cycle of heme peroxidases involves two reactive states, compound I and compound II. Although their reduction potentials at pH 7 are similar, compound I is in general more reactive towards organic substrates than compound II. The different reactivities have until now remained unexplained. In this study, the reactions of compounds I and II of peroxidase from horseradish with phenols were analyzed using the Marcus equation of electron-transfer. Both reactions exhibit similar reorganization energies, and the different reactivities of the two enzyme states can be ascribed to a higher apparent rate of activationless electron-transfer in the compound I reactions. This can be attributed to the shorter electron-tunneling distance on electron-transfer to the porphyrin radical cation in compound I, compared to electron-transfer to the iron ion in compound II.

【 授权许可】

Unknown