title: Heterogeneity of the Type 3 copper in Japanese-lacquer-tree (Rhus vernicifera) laccase.
abstract: The two steps of the titration of the Japanese-lacquer-tree (Rhus vernicifera) laccase with N3- [Morpurgo, Rotilio, Finazzi-Agrò & Mondovi (1974) Biochim. Biophys. Acta 336, 324-328; LuBien, Winkler, Thamann, Scott, Co, Hodgson & Solomon (1981) J. Am. Chem. Soc. 103, 7014-7016] were shown to be two distinct reactions, each involving one different portion of the native enzyme molecules. The difference consists in the oxidation state of the Type 3 Cu, which is reduced in the portion with higher affinity for N3- and oxidized in the portion with lower affinity for N3-. The difference is eliminated by treatment with oxidizing (H2O2) or reducing agents, and a single N3- adduct is then formed. The e.p.r. spectra of the H2O2-treated enzyme and of its F- derivatives support this interpretation of the results. The similarity of the spectroscopic properties of the high-affinity N3- adduct to those of the N3- adducts of half-met-haemocyanins and half-met-tyrosinase is discussed.
mesh_terms: D001386:Azides / Q000494:pharmacology; D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D042845:Laccase; D010088:Oxidoreductases / Q000378:metabolism*; D010947:Plants, Toxic; D019810:Sodium Azide; D012969:Sodium Fluoride / Q000494:pharmacology; D012251:Toxicodendron / Q000201:enzymology*
chemical_list: D001386:Azides; D003300:Copper; D012969:Sodium Fluoride; D019810:Sodium Azide; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D042845:Laccase