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The thermodynamics and kinetics of electron transfer in the cytochrome P450 cam enzyme system
Author(s) -
Honeychurch Michael J,
Hill H.Allen O,
Wong Luet-Lok
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00610-9
Subject(s) - electron transfer , chemistry , substrate (aquarium) , kinetics , electron transport chain , cytochrome , marcus theory , thermodynamics , crystallography , photochemistry , reaction rate constant , enzyme , organic chemistry , biochemistry , physics , oceanography , quantum mechanics , geology
In anaerobic environments the first electron transfer in substrate‐free P450 cam is known to be thermodynamically unfavourable, but in the presence of dioxygen the reduction potential for the reaction shifts positively to make electron transfer thermodynamically favourable. Nevertheless a slower rate of electron transfer is observed in the substrate‐free P450 cam compared to substrate‐bound P450 cam . The ferric haem centre in substrate‐free P450 cam changes from six co‐ordinate to five co‐ordinate when reduced whereas in substrate‐bound P450 cam the iron centre remains five co‐ordinate in both oxidation states. The slower rate of electron transfer in the substrate‐free P450 cam is therefore attributed to a larger reorganisation energy as predicted by Marcus theory.