Rhus vemicifera

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

Raman spectra, 6,652 kinetic studies, 6,699 Rhus vemicifera spectra, 6,652 type 2-depleted, 6,699 (3-Lactam antibiotics bacterial resistance, 6,462 (3-Lactamases zinc, 6, 612 Lactams hydrolysis... 

The blue copper protein stellacyanin, with a molecular weight of about 20,000, is obtained from the Japanese lacquer tree Rhus vemicifera. The EPR spectrum is described by roughly axial g and ACu hfs tensors and an unusually small a j value. As shown in Fig. 39 a, only the largest copper hf value A u can be directly determined from the EPR spectrum202. This coupling does not lie along the largest g-principal axis, in contrast to the usual behaviour of square planar copper complexes. 

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)... 

Stellacyanin from Rhus vemicifera is less well studied. The polypeptide does not contain a methionine residue showing that the ligands of the type 1 site may vary. There is EXAFS evidence for a short Cu—S(Cys) bond,920 while UV, visible and near IR studies confirm similarities with the other blue proteins. It has been suggested that methionine is replaced as a ligand by an —S—S— group. This is based on resonance Raman921 and NMR studies.922... 

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...

The recovery of the sap from the tree Rhus vemicifera to obtain urushiol has been described in the classical process (ref. 184, 185) and with regard to recent developments (ref. 186). It is a totally different operation from that with Anacardium occidentale, and not unlike that in the process for natural rubber. The name derives from kiurushi, the Japanese word for sap which is a primary product of the tree. Much less of this very ancient material is now processed in the original region of Sendai, Japan and the main industry is based in China with some in Korea and Japan. In northern Vietnam and Taiwan, a source of lac is Rhus succedanea and in Thailand and Burma, Melanorrhoea usitata. 

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 ). 

GLC retention data proved useful in showing that Rhus vemicifera (from Japan) contains a small proportion of the 8,11,14-triene (ref. 89) in addition to the main 8,11,13- constituent. In Rhus toxicodendron the unsaturation is found at the 8 8,11 and 8, 11,14-positions as in the cashew phenols (ref. 228). 

A number of applications of commercial lacs and of separated urushiol have been referred to (ref. 2). As with the phenolic lipids of Anacardium occidentale a great deal of work has been carried out particularly in Japan and China to diversify the uses of lacs from Rhus vemicifera. It is widely employed in artistic decoration, building materials, textile equipment and furniture. The industrial utilisation of polyketide natural products including the phenolic lipid urushiol has been reviewed (ref. 314). The great number of uses largely comprise polymerisation reactions and some non-polymeric processes, some of both of which are described in the next sections. 

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). 

Japanese Lacquer Films Lacquers are used ubiquitously as surface-coating materials for wood, porcelain, and metal. The main component of Japanese lacquer ( ura-shi in Japanese) is urashiol, a brown liquid (boiling point, 200-210 °C) consisting of a mixture of several catechols, each substituted with a satmated or unsaturated alkyl chain of 15 or 17 carbon atoms [55]. The liquid that causes an allergic skin reaction in most people, is obtained from the sap of the Japanese lacquer tree (Rhus vemicifera) and can be polymerized to form lacquer films. Lacquer films have been... 

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. 

Concurrently, the Egyptians, Japanese, and Chinese were beginning to develop lacquers (Stillman, I960). Some time before 200 b.c., the Chinese used the exudation (sap) from the conifer Rhus vemicifera (which became known as the sumac or varnish tree) as a coating. This plant has also been called the urushi tree. The tree belongs to the same family as the poison ivy plant, and like it, all parts of the tree are toxic— tree, sap, and latex. Those who tap the tree must wear gloves and protective clothing. The active irritant is urushiol, a catechol derivative. 

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