title: Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II).
abstract: Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II) were investigated by absorption and e.s.r. spectroscopy. When native laccase was treated with excess hexacyanoferrate(II), the type-1 and type-2 coppers were immediately reduced and the e.s.r. signal due to type-3 copper was transiently observed. After incubation, a novel e.s.r. signal (g parallel = 2.31, g perpendicular = 2.08) developed together with the type-1 copper signal. Only the novel e.s.r. signal was left after the sample had been treated with ascorbate. In the corresponding absorption spectrum, a new band was observed at around 490 nm. A similar new e.s.r. signal did not appear for the type-2-copper-depleted (T2D) laccase, in which the type-3 copper had been reduced during the procedure to deplete the type-2 copper. On the other hand, the novel e.s.r. signal emerged when the type-3 copper in T2D laccase had been previously reoxidized with H2O2. The novel e.s.r. signal was not significantly saturated even by 200 mV microwave power at 4 K. Quantitative estimations and a small molecule study for CuII-FeII(CN)6 and CuII-FeIII(CN)6 systems suggested that the novel e.s.r. signal corresponds to some sort of adduct involving the type-3 copper and hexacyanoferrate(II).
authors.affiliation: College of Liberal Arts and Sciences, Kanazawa University, Ishikawa, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sakurai
mesh_terms: D000693:Anaerobiosis; D003300:Copper / Q000378:metabolism* / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005295:Ferrocyanides / Q000494:pharmacology*; D007700:Kinetics; D042845:Laccase; D010088:Oxidoreductases / Q000378:metabolism*; D010947:Plants, Toxic; D012251:Toxicodendron / Q000201:enzymology*
chemical_list: D005295:Ferrocyanides; D003300:Copper; D010088:Oxidoreductases; D042845:Laccase; C020354:hexacyanoferrate II