Rhus vernicifera

A crude process of extraction of urushiol from the tree Rhus vernicifera was used by the Chinese during the Chou dynasty of 1122-249 BC, and the process was systematised by the Japanese. The tree is tapped at about the 10th year of cultivation by a lateral sloping incision into the bark during June to September. The sap is white to grayish in color, but on exposure to air turns yellow-brown and then black. The crude sap contains approximately 70% urushiol, 4% gum, 2% albuminous materials, and 24% water. It is stirred and filtered and heated to reduce the moisture level [138] and finally stored in air-tight containers. 

Thiobacillus ferrooxidans function. 6, 651 Rhus vernicifera stellacyanin structure, 6,651 Riboflavin 5 -phosphate zinc complexes, 5,958 Ribonucleotide reductases cobalt, 6,642 iron, 6,634... 

Another interesting blue protein is stellacyanin (FW = 20 000) from the Japanese lacquer tree Rhus vernicifera, in which, with respect to the other cupredoxins, glutamine replaces the methionine ligand.64 Stellacyanin also bears an overall positive charge (p/=9.9). It, therefore, gives a reversible Cu(II)/Cu(I) response at a glassy carbon electrode in aqueous solution (pH 7.6).61 The formal electrode potential of the Cu(II)/Cu(I) reduction (E01 = + 0.18 V vs. NHE) is the lowest among cupredoxins. 

The same model has been used to fit the data obtained for the reactions of azurin, Az(Cu(I)) and Rhus vernicifera stellacyanin, St(Cu(I)), with Cr(III)(phen)3 and Ru(II)(bpy)3 oxidants. Values of the rate constants kt and stability constants K and K2 of the 1 1 and 2 1 complexes that have been extracted from the analyses are given in Table 2. 

Visible MCD spectra of plastocyanin, azurin, Rhus vernicifera laccase, ascorbate oxidase and ceruloplasmin are similar on a per copper basis, but show differences from those of stellacyanin and fungal laccase. This is of interest in view of the absence of methionine from the coordination sphere of copper in stellacyanin, and the very high redox potential of fungal laccase.925... 

Co(II) has been the most useful metal probe for the study of BCE The Co(II) derivatives of Ps. aeruginosa azurin (Moratal Mascarell et al., 1993a Piccioli et al., 1995 Salgado et al., 1995), Rhus vernicifera stellacyanin (Fernandez et al., 1997 Vila, 1994 Vila and Fernandez, 1996), Ac. cyclo-clastes pseudoazurin (Fernandez et al., 2001), Thi. ferrooxidans rusticyanin (Donaire et al., 2001), Thi. versutus amicyanin (Salgado et al., 1999), several mutants of azurin (Piccioli et al., 1995 Salgado et al., 1996, 1998a Vila et al., 1997), and the M99Q mutant of amicyanin (Diederix et al., 2000) have been prepared, and their H NMR spectra have been characterized. 

Cu-O-(Gln) bond of 2.21 A in the 1.6 A structure and 2.36 A in the newly refined 1.2 A structure. This bond lengthens to 2.5 A in the structure of the reduced protein at 1.45 A resolution (Figure 6d). The spectroscopic properties of cucumber stellacyanin are nearly identical to that of the protein from Rhus vernicifera ... 

Urushiol is the liq secretion of Rhus vernicifera used in Japan lacquer. It contains an unbranched, OH imsaturated side chain in the... 

Laccase, 1.10.3.2, Rhus vernicifera, Coriolus hirsitus, Polyporus versicolor... 

The redox potential of the Tl Cu-site has been determined using potentiometric titrations with redox mediators for a large number of different laccases and varies between 410 mV vs. NHE for Rhus vernicifera [67] and 790 mV for laccases from Polyporus versicolor and Coriolus hirsutus [244,251]. The T2 and T3 sites have higher potentials [251]. 

Laccase contains four copper atoms and catalyzes the four-electron reduction of dioxygen to water. X-Ray absorption edge spectroscopy has been used to determine the oxidation states of copper in Rhus vernicifera laccase, following the reaction of the reduced enzyme with dioxygen (202). This study included the incorporation of mercury(II) in the Type 1 copper site (see Section IV,B). The results demonstrate that the Type 2/Type 3 trinuclear copper site, as found in ascorbate oxidase (103), represents the minimal active site required for the multielectron reduction of dioxygen. 

Self-exchange rate constants have been determined for P. aeruginosa and A. dinitrificans azurin (63) and T. versutus amicyanin (68) by NMR line broadening, and for Rhus vernicifera stellacyanin by EPR... 

Pyrolysis also has been utilized for the determination of the structure of unique natural polymers in certain lacquers such as those produced by Rhus vernicifera and Rhus succedanea [2] and utilized as surface coating for wood, porcelain, etc. in Japan. The pyrolysis products of the two lacquer films at 400° C contain respectively laccol and urushiol, and each also contains alkenes, alkanes, alkenylphenols, and alkylphenols. From these results it was possible to assign the following structure for laccol polymer ... 

Faced with the problem of elucidating the individual roles of the diflFerent copper centers in the blue oxidases, the researcher has naturally focused in recent years on the laccases (9). Being easier to isolate, better characterized, and containing fewer copper atoms than cemloplasmin or ascorbate oxidase, the laccases from the Japanese lacquer tree Rhus vernicifera and the fungus Polyporus versicolor have been the subject of several transient kinetic studies in the millisecond range, that is, studies using stopped-flow spectrophotometry and rapid-freeze EPR spectroscopy (9,49,50). 

Coniferyl alcohol was polymerized by laccase catalyst. The polymerization behavior depended on the origin of the enzyme. PCL and laccase from Coriolus versicolar showed high catalytic activity to give the dehydrogenative insoluble polymer, whereas very low catalytic activity was observed in laccase from Rhus vernicifera Stokes.54 The increase of the molecular weight was observed in the treatment of soluble lignin using TVL catalyst.82... 

Group 11. Paramagnetic (1H, 15N) NMR spectra were used to study a Cu -IDA (=iminodiacetic acid) complex localised on a protein surface. H and 13C NMR spectra were reported for copper(II) bis-benzimidazole complexes.1225 Variable temperature H NMR spectra of copper complexes of p-octafluorinated triarylcorroles reveal a thermally-accessible paramagnetic excited state, i.e. a Cu11 corrole 7i-cation radical.1226 Copper(II) forms of stellacyanin from Rhus vernicifera were characterised by H NMR.1227... 

Johnson, D.L, Thompson, J.L., Brinkmann, S.M., Schuller, K.A., and Martin, L.L. (2003) Electrochemical characterization of purified Rhus vernicifera laccase voltammetric evidence for a sequential four-electron transfer. Biochemistry, 42 (34). 10229-10237. 

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