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Intramolecular electron transfer in laccases
Author(s) -
Farver Ole,
Wherland Scot,
Koroleva Olga,
Loginov Dmitry S.,
Pecht Israel
Publication year - 2011
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2011.08268.x
Subject(s) - laccase , chemistry , electron transfer , reaction rate constant , multicopper oxidase , intramolecular force , trametes versicolor , stereochemistry , organic chemistry , kinetics , enzyme , physics , quantum mechanics
Rate constants and activation parameters have been determined for the internal electron transfer from type 1 (T1) to type 3 (T3) copper ions in laccase from both the fungus Trametes hirsuta and the lacquer tree Rhus vernicifera , using the pulse radiolysis method. The rate constant at 298 K and the enthalpy and entropy of activation were 25 ± 1 s −1 , 39.7 ± 5.0 kJ·mol −1 and −87 ± 9 J·mol −1 ·K −1 for the fungal enzyme and 1.1 ± 0.1 s −1 , 9.8 ± 0.2 kJ·mol −1 and −211 ± 3 J·mol −1 ·K −1 for the tree enzyme. The initial reduction of the T1 site by pulse radiolytically produced radicals was direct in the case of T. hirsuta laccase, but occured indirectly via a disulfide radical in R. vernicifera . The equilibrium constant that characterizes the electron transfer from T1 to T3 copper ions was 0.4 for T. hirsuta laccase and 1.5 for R. vernicifera laccase, leading to full reduction of the T1 site occurring at 2.9 ± 0.2 electron equivalents for T. hirsuta and 4 electron equivalents for R. vernicifera laccase. These results were compared with each other and with those for the same process in other multicopper oxidases, ascorbate oxidase and Streptomyces coelicolor laccase, using available structural information and electron transfer theory. Database
Protein structure data for Trametes hirsuta laccase are available in the wwPDB database under the accession number 3FPX . Sequence references are Q94ID0 for Rhus vernicifera laccase and B2L9C1 for Trametes hirsuta laccase