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

• Published in: Biochemical journal Vol. 187; no. 2; pp. 361 - 366
• Main Authors: Morpurgo, L, Graziani, M.T, Finazzi-Agro, A, Rotilio, G, Mondovi, B
• Format: Journal Article
• Language: English
• Published: England 01.05.1980
• Subjects: Circular Dichroism; Copper - analysis; Laccase; Oxidation-Reduction; Oxidoreductases; plant biochemistry; plant physiology; Plants - enzymology; Plants, Toxic; Spectrometry, Fluorescence; Spectrophotometry; Toxicodendron - enzymology
• ISSN: 0306-3275; 0264-6021; 1470-8728
• DOI: 10.1042/bj1870361

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.