マルチ銅酸化酵素研究における分光法、電子構造と電子機能

概要

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In this review, current development of studies on electronic structures of the copper active sites of multicopper oxidase (MCO) by various spectroscopic methods and related electronic functions have been reported by comparing with related metalloenzyme. In particular, physical meanings of parameters derived from spectroscopic data were emphasized to discuss electronic structures. The family of MCO catalyzes the 4 electron reduction of molecular oxygen to water with concomitant 1 electron oxidation of substrates. The electrons are transferred about 13 Å from one type 1 (T1) "blue" Cu site to the trinuclear oxygen reduction Cu site comprised of a type 2 (T2) "normal" Cu and a type 3 (T3) "coupled binuclear" Cu site, where two Cu(II) atoms are antiferromagnetically couples by a bridging hydroxide ligand. The electronic structures of the trinuclear sites in the ground and/or excited states are investigated mainly by electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) to prove (i) spin frustrated ground state of an antiferromagnetically coupled trinuclear system and (ii) covalency of Cu-S coordination bonds derived from ligand-to-metal charge transfer excited state.