Rhus vemicifera laccases

Fig. 38. Optical absorption spectra (room temperature) of native Rhus vemicifera laccase and native + low 10-fold excess) concentration NJ, high (3100-fold excess) concentration NJ and 30-fold excess peroxide, dialyzed. EPR spectra (77 K v = 9.1 GHz) of native, native + low concentration NJ and native + high concentration NJ...

Rhus vemicifera Laccase. The physical and chemical properties of Rhus laccase and fungal laccase may be compared in Table 2. It is clear that while there are differences in the gross physical properties such as molecular weight, carbohydrate content, and amino acid composition, nature has preserved a four-Cu complex capable of accepting four electrons (77—79) consisting of one Type 1 Cu2+, and one Type 2 Cu2+, and the Type 3 pair. There are other minor differences reflected in the comparable redox potentials, g values, and other detailed spectroscopic parameters but on the whole the state and function of Cu bound to Rhus laccase would seem to be identical with Polyporus laccase (cf. Fig. 3). 

Kau LS, Spira-Soloman DJ, Penner-Hahn JE, Hodgson KO, Solomon El. X-ray absorption edge determination of the oxidation state and coordination number of copper. Application to the type 3 site in Rhus vemicifera laccase and its reaction with oxygen. J Am Chem Soc 1987 109 6433-6442. 

Augustine AJ, Kragh ME, Sarangi R, Fujii S, Liboiron BD, Stoj CS, Kosman DJ, Hodgson KO, Hedman B, Solomon El. Spectroscopic studies of perturbed T1 Cu sites in the multicopper oxidases Saccharomyces cerevisiae FetSp and Rhus vemicifera laccase allosteric coupling between the T1 and trinuclear Cu sites. Biochemistry 2008 47 2036-2045. 

On adding dioxygen to the fully reduced laccase of the lacquer tree Rhus vemicifera, the type-1 Cu and the type-3 Cu-pair were oxidized in the ms range and an optical intermediate was observed at 360 nm At liquid helium temperatures an EPR signal was observed, which was tentatively interpreted as due to O ", as a result of its very short relaxation time and of the increase of its linewidth when the reduced laccase of the fungus Polyporus versicolor was treated with 0 A similar paramagnetic oxygen intermediate was also observed with the laccase of another lacquer tree Rhus succedanea and with ceruloplasmin. The decay of the intermediate at 25 °C (tj = 1 s at pH 5.5 with R. succedanea laccase) was accompanied by the reoxidation of the type-2 Cu >. One would expect, however, such an intermediate to be extremely reactive (See Sect. 3.3), while it was stable in tree laccase depleted of type-2 Cu(II)... 

The sap from Rhus vemicifera by extraction with light petroleum affords urushiol a mixture which is considerably more sensitive to oxidative deterioration and polymerisation than the cashew phenols since it is both a catechol and even more highly unsaturated. The composition of the sap is to some extent dependent on the source but typically it contains urushiol (55-65%), water (20-30%), glycoprotein (2-3%), polysaccharides (5-7%) and laccase (-c 1%) (ref. 196 ). 

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