title: Optical properties of japanese-lacquer-tree (Rhus vernicifera) laccase depleted of type 2 copper(II). Involvement of type-2 copper(II) in the 330nm chromophore.
abstract: 1. Spectroscopic and functional properties of Japanese-lacquer-tree (Rhus vernicifera) laccase were re-investigated, with special emphasis on the relationships between the different types of copper centres (Types 1, 2, and 3). 2. On removal of the Type 2 Cu(II),  a decrease of absorbance occurred in the wavelength region above 650 nm (delta epsilon 750 = 300 M-1 . cm-1) and around 330 nm (delta episom 330 up to 2200 M-1 . cm-1). 3. Reductive titrations with ascorbic acid or ferrocyanide showed that the electron-accepting capacity of the partial apoprotein is one electron-equivalent lower than that of the native protein, i.e. the protein two-electron acceptor is present in the oxidized state in spite of absorbance loss at 330 nm. 4. The 330 nm chromophore apparently depends on the presence of both the Type 2 and the Type 3 copper in the oxidized state. 5. This finding may have implications in the relative location of Type 2 and 3 copper centres and on the redox behaviour of laccase.
mesh_terms: D002942:Circular Dichroism; D003300:Copper / Q000032:analysis; D042845:Laccase; D010084:Oxidation-Reduction; D010088:Oxidoreductases; D010944:Plants / Q000201:enzymology*; D010947:Plants, Toxic; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D012251:Toxicodendron / Q000201:enzymology
chemical_list: D003300:Copper; D010088:Oxidoreductases; D042845:Laccase