title: Intramolecular Electron Transfer in the Bacterial Two-Domain Multicopper Oxidase mgLAC.
abstract: The kinetics of the intramolecular electron transfer process in mgLAC, a bacterial two-domain multicopper oxidase (MCO), were investigated by pulse radiolysis. The reaction is initiated by CO2(-) radicals produced in anaerobic, aqueous solutions of the enzyme by microsecond pulses of radiation. A sequence of pulses of CO2(-) radicals enables examination of the reductive half-cycle of the MCO catalysis. This is done by titrations of the Type 1 (T1) Cu(II) site and monitoring of the time course and amplitude of its reoxidation by internal electron transfer (ET) to the Type 3 site. Comparison of the internal ET kinetics observed for mgLAC with those of other MCOs studied by pulse radiolysis shows that they exhibit distinct reactivities. One main cause for the different reactivities is the broad range of T1 copper redox potentials, from the moderate potential of bacterial enzymes to the high potential of fungal laccases, and this possibly also reflects evolutionary quaternary structural adaptation of the MCO family to the wide range of reducing substrates that they oxidize while maintaining efficient reduction of the common substrate, molecular oxygen.
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164-4630, United States.
authors.forename: Scot
authors.initials: S
authors.lastname: Wherland
authors.affiliation: Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology , Tsukuba Central 6, 10101 Higashi, Tsukuba, Ibaraki 205-8566, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Miyazaki
authors.affiliation: Department of Immunology, Weizmann Institute of Science , Rehovot 76100, Israel.
authors.forename: Israel
authors.initials: I
authors.lastname: Pecht
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004579:Electron Transport; D004583:Electrons; D007700:Kinetics; D042845:Laccase / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D011675:Pulse Radiolysis; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D003300:Copper; D010088:Oxidoreductases; D042845:Laccase