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At least 109 records · Page 6Linked to original sources
PubMed1982

Heterogeneity of the Type 3 copper in Japanese-lacquer-tree (Rhus vernicifera) laccase.

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.

Azides↗
PubMed1983

Yeast copper-thionein can reconstitute the Japanese-lacquer-tree (Rhus vernicifera) laccase from the Type 2-copper-depleted enzyme via a direct copper(I)-transfer mechanism.

The Type 2-Cu-depleted laccase from the Japanese lacquer tree (Rhus vernicifera) can be reconstituted with CuSO4 aerobically and much more rapidly and efficiently under anaerobic reducing conditions. This is to be related to a more favourable conformation of a laccase in the reduced state, rather than to reduction of the metal ion. In fact, reconstitution with Cu(I)-thionein from baker's yeast (Saccharomyces cerevisiae) only proceeds under anaerobic reducing conditions, via a direct transfer of Cu(I).

Binding Sites↗
PubMed1983

Low-temperature resonance-Raman spectra of Japanese-lacquer-tree (Rhus vernicifera) laccase, type-2-copper-depleted laccase and H2O2-treated type-2-copper-depleted laccase.

Resonance-Raman spectra of Japanese-lacquer-tree (Rhus vernicifera) laccase, type-2-copper-depleted laccase and the latter form treated with H2O2 were measured in liquid and frozen solution, on excitation into the 600 nm absorption band. Significant changes in intensity and/or frequency of the bands lying in the 370-430 cm-1 region were observed on freezing, indicating local structural rearrangements taking place at the blue copper site. These findings corroborate previous suggestions based on e.p.r. measurements and redox data [Morpurgo, Calabrese, Desideri & Rotilio (1981) Biochem. J. 193, 639-642]. They show the strong dependence of the physical properties of blue copper centres on local symmetry. Some conclusions on the origin of the Raman bands are also drawn.

Cold Temperature↗
PubMed1992

Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II).

Anaerobic reactions of Rhus vernicifera laccase and its type-2 copper-depleted derivatives with hexacyanoferrate(II) were investigated by absorption and e.s.r. spectroscopy. When native laccase was treated with excess hexacyanoferrate(II), the type-1 and type-2 coppers were immediately reduced and the e.s.r. signal due to type-3 copper was transiently observed. After incubation, a novel e.s.r. signal (g parallel = 2.31, g perpendicular = 2.08) developed together with the type-1 copper signal. Only the novel e.s.r. signal was left after the sample had been treated with ascorbate. In the corresponding absorption spectrum, a new band was observed at around 490 nm. A similar new e.s.r. signal did not appear for the type-2-copper-depleted (T2D) laccase, in which the type-3 copper had been reduced during the procedure to deplete the type-2 copper. On the other hand, the novel e.s.r. signal emerged when the type-3 copper in T2D laccase had been previously reoxidized with H2O2. The novel e.s.r. signal was not significantly saturated even by 200 mV microwave power at 4 K. Quantitative estimations and a small molecule study for CuII-FeII(CN)6 and CuII-FeIII(CN)6 systems suggested that the novel e.s.r. signal corresponds to some sort of adduct involving the type-3 copper and hexacyanoferrate(II).

Anaerobiosis↗
PubMed1995

Stability of Japanese-lacquer-tree (Rhus vernicifera) laccase to thermal and chemical denaturation: comparison with ascorbate oxidase.

The thermal denaturation of laccase from the Japanese lacquer tree (Rhus vernicifera) was studied by differential scanning calorimetry. The endotherms of holo-laccase, type 2-Cu-depleted laccase and apo-laccase were deconvoluted into two independent two-state transitions, providing evidence for a domain structure of the protein. The correlation of the two transitions with the bleaching of copper optical bands and the decrease of the transitions' enthalpy on Cu removal show that the process involves the denaturation of Cu sites. No detectable unfolding of secondary structure was observed, since the thermal transitions, characterized by low overall specific enthalpy, did not modify either the laccase c.d. spectra in the beta-fold region or the maximum wavelength of the fluorescence emission. On chemical denaturation, however, the emission was red-shifted by about 20 nm. The laccase behaviour is substantially different from that of stellacyanin, a protein containing a single blue Cu ion, in which the thermal transition had higher specific enthalpy and induced a large change of the c.d. spectrum in the beta-fold region. The laccase denaturation behaviour is similar to that of ascorbate oxidase from zucchini (courgette; Cucurbita pepo) [Savini, D'Alessio, Giartosio, Morpurgo and Avigliano (1990) Eur. J. Biochem. 190, 491-495], suggesting a structural analogy. In both proteins heating may cause a change of tertiary structure through modifications of Cu co-ordination with loosening of the bonds between the structural domains at the interface of which the trinuclear Cu cluster is located.

Ascorbate Oxidase↗
PubMed2000

Spatial distribution of allozyme polymorphisms following clonal and sexual reproduction in populations of Rhus javanica (Anacardiaceae).

Rhus javanica L. (Anacardiaceae), a dioecious tree with both sexual reproduction and clonal growth, is widely distributed in warm temperate, subtropical, and tropical regions in east Asia. We used allozyme loci and spatial autocorrelation statistics to examine clonal structure and the spatial distribution of allozyme polymorphisms in two Korean populations. Populations of the species maintain moderate levels of allozyme variability (mean He=0.175, GST=0.060), and high levels of multilocus genotypic diversity (mean DG=0.971). Clone-pair distances ranged from 1.4 m to 57.4 m, and had high mean values of 24.0 m and 25.6 m in the two study populations. Approximate genetic patch widths were inferred to be 23-25 m. The results indicated that within populations there is moderate (one study population) or no (other study population) spatial genetic structure among sexually reproduced individuals, and vegetatively reproduced genotypes also are almost randomly distributed. The spatial genetic structure among sexually reproduced trees in the one case is probably caused by limited pollen dispersal in that population, and the lack of structure in the other probably results from the short time elapsed since founding. It appears that clonal reproduction also does not contribute substantially to genetic isolation by distance neither among the sexually reproduced individuals nor the total population. Ramets often establish long distances from their progenitors and thus do not substantially increase the degree of local consanguineous matings.

Genetic Markers↗
PubMed1999

Assessment of the ability of the topical skin protectant (TSP) to protect against contact dermatitis to urushiol (Rhus) antigen.

BACKGROUND: Military personnel have a need for effective protection against cutaneous exposure to chemical warfare agents (CWA). Topical Skin Protectant (TSP) is being developed to supplement chemical warfare protective garments. TSP protects against CWA exposure in animals, but does it work for humans? Because humans should not be tested with live CWA, urushiol (poison ivy) extract was used as a surrogate substance in place of CWA for human efficacy testing of TSP. OBJECTIVE: Determine whether TSP protects human skin against experimentally-induced urushiol dermatitis. METHODS: Open urushiol patch testing of 50 rhus-sensitive subjects comparing the 96-hour dermatitis severity scores between TSP protected and TSP unprotected sites. There were 4 paired sites (i.e., protected versus unprotected) per subject. Test sites were scored using a 9-point dermatitis scale of 0.0 to 4.0 (using 0.5 increments). RESULTS: Analysis of variance of the dermatitis scores from 192 paired sites on 48 evaluable subjects showed that TSP protected sites had mean dermatitis scores about 2 points lower than TSP unprotected sites (P <.001). CONCLUSION: Although this study does not provide direct scientific evidence that TSP protects humans against the percutaneous absorption of CWA, it does provide circumstantial evidence that this is the case. The fact that TSP is so highly effective against a lipophilic substance like urushiol and that most common vesicant CWAs are lipophilic and are weaponized in oleaginous vehicles, makes the effectiveness of TSP in preventing absorption and dermatitis from CWA seem likely.

Adolescent↗
PubMed2001

Cardanols from leaves of Rhus thyrsiflora.

A mixture of 3-substituted alkyl- and alkenylphenols including nine new compounds (cardanols) was isolated from leaves of the Yemenian plant Rhus thyrsiflora (Anacardiaceae) and identified by GC-MS. The position of the double bond in the compounds bearing a monolefinic side chain was determined by their typical MS fragmentation patterns after hydroxylation and trimethylsilylation.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

6-Pentadecylsalicylic acid: an antithrombin component isolated from the stem of Rhus semialata var. roxburghii.

Bioassay-directed fractionation of the n-hexane extract of the stem of Rhus semialata Murr. var. roxburghii DC (Anacardiaceae) has led to the isolation of 6-pentadecylsalicylic acid. It showed antithrombin activity at 50 micrograms/ml in the amidolytic method. It also prolonged the clotting time in a dose-dependent manner in the clotting assay of thrombin-fibrinogen interaction.

Amino Acid Sequence↗
PubMed1989

Hinokiflavone, a cytotoxic principle from Rhus succedanea and the cytotoxicity of the related biflavonoids.

Hinokiflavone (1) was isolated as the cytotoxic principle from the drupes of Rhus succedanea L. A comparison of the cytotoxicity of 1 and other related biflavonoids, including amentoflavone (2), robustaflavone (3), agathisflavone (4), rhusflavone (5), rhusflavanone (6) and its hexaacetate (7), succedaneaflavanone (8) and its hexaacetate (9), cupressuflavone (10), neorhusflavanone (11), volkensiflavone (12) and its hexamethyl ether (13), spicataside (14) and its nonaacetate (15), morelloflavone (16) and its heptaacetate (17) and heptamethyl ether (18), GB-1a (19) and its hexamethyl ether (20) and 7"-O-beta-glucoside (21), and GB-2a (22), indicates that an ether linkage between two units of apigenin as seen in 1 is structurally required for significant cytotoxicity. Compounds 13 and 20 also demonstrated significant cytotoxicity.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Spectroscopic and kinetic studies on the oxygen-centered radical formed during the four-electron reduction process of dioxygen by Rhus vernicifera laccase.

The oxygen-centered radical bound to the trinuclear copper center was detected as an intermediate during the reoxidation process of the reduced Rhus vernicifera laccase with dioxygen and characterized by using absorption, stopped-flow, and electron paramagnetic resonance (EPR) spectroscopies and by super conducting quantum interface devices measurement. The intermediate bands appeared at 370 nm (epsilon approximately 1000), 420 nm (sh), and 670 nm (weak) within 15 ms, and were observable for approximately 2 min at pH 7.4 but for less than 5 s at pH 4.2. The first-order rate constant for the decay of the intermediate has been determined by stopped-flow spectroscopy, showing the isotope effect, k(H)/k(D) of 1.4 in D(2)O. The intermediate was found to decay mainly from the protonated form by analyzing pH dependences. The enthalpy and entropy of activation suggested that a considerable structure change takes place around the active site during the decay of the intermediate. The EPR spectra at cryogenic temperatures (<27 K) showed two broad signals with g approximately 1.8 and 1.6 depending on pH. We propose an oxygen-centered radical in magnetic interaction with the oxidized type III copper ions as the structure of the three-electron reduced form of dioxygen.

Binding Sites↗
PubMed2001

A novel mixed valence form of Rhus vernicifera laccase and its reaction with dioxygen to give a peroxide intermediate bound to the trinuclear center.

Rhus vernicifera laccase, in a novel mixed valence state [T1oxT23red: type 1 Cu as Cu(II), and type 2 and 3 Cus as Cu(I)], was formed by reacting Cu(I) on the type 2 Cu-depleted laccase [T1oxT3red: type 1 Cu as Cu(II) and type 3 Cus as Cu(I)] under argon. Contrary to T1oxT3red, T1oxT23red was highly reactive with dioxygen, and gave the three transient bands at 340, 475, and 680 nm due to the two-electron reduced form of dioxygen [charge transfer bands from peroxide to Cu(II)]. The first order decays were highly dependent on pH, which led to the successful detection of the intermediate for ca. 2 h at pH 7.5. Another mixed valence derivative, T12oxT3red [type 1 and type 2 Cus as Cu(II), and type 3 Cus as Cu(I)] prepared through the action of Cu(II) on T1oxT3red was not reactive with dioxygen, but showed high enzyme activity as to the oxidation of N,N-dimethyl-p-phenylenediamine. The whole reaction mechanism of the reduction of dioxygen by laccase was proposed based on the present results together with data for the former detection and characterization of the three-electron reduced form of dioxygen [Huang, H. et al. (1999) J. Biol. Chem. 274, 46, 32718-32724].

Binding Sites↗
PubMed1990

pH and microwave power effects on the electron spin resonance spectra of Rhus vernicifera laccase and Cucumis sativus ascorbate oxidase.

The present study shows that the electron spin resonance (ESR) spectral features of Rhus laccase depend considerably on the pH value of the enzyme solution and the irradiated microwave power. Because of the local protein structure change, the type 1 copper is appreciably autoreduced at alkaline pH as monitored both by the ESR and absorption spectroscopies. In addition, the ESR signal of the type 2 copper, especially its g perpendicular region, becomes prominent at alkaline pH. Protein dissociation from a water or an imidazole group coordinated to the type 2 copper is supposed to be responsible for this behavior. Besides above pH effects, the g perpendicular component of the type 2 copper ESR signal is obscured with rising microwave power level. The power saturation behavior of native laccase and its derivatives reveals that the type 2 copper is more easily saturated than the type 1 copper. Cucumis ascorbate oxidase also exhibits similar behavior upon pH variation and microwave power saturation.

Ascorbate Oxidase↗
PubMed1986

The failure of immunotherapy with dinitrochlorobenzene and Rhus extract for recurrent conjunctival squamous papillomas.

A 25-year-old white male is described who presented with recurrent conjunctival squamous papillomata. Despite prior reports of successful dinitrochlorobenzene use for tropical immunotherapy, its failure in our patient, and the first documented attempt to employ Rhus oleoresin (poison ivy/oak) extract for topical conjunctival immunotherapy is reported. The role of topical immunotherapy in treating recurrent conjunctival papillomas is discussed.

Administration, Topical↗
PubMed1999

Anatomy of two mechanisms of breaking physical dormancy by experimental treatments in seeds of two North American Rhus species (Anacardiaceae).

Anatomy of the endocarp was studied in relation to the physical dormancy-breaking mechanisms in experimentally treated Rhus aromatica var. aromatica and R. glabra germination units, which include seed plus endocarp (hereafter seeds). The endocarp has three distinct layers, with brachysclereids on the outside, osteosclereids in the middle, and macrosclereids on the inside. Brachysclereids in the carpellary micropyle region (i.e., region immediately adjacent to the integumentary micropyle) are shorter than those in other parts of the endocarp, and the macrosclereids in this region are not elongated. Thus, a weak point is formed in the endocarp. Concentrated sulfuric acid broke seed dormancy in R. aromatica by eroding the brachysclereids and osteosclereids in the carpellary micropyle region, whereas boiling water broke dormancy in seeds of R. glabra by inducing a blister adjacent to the carpellary micropyle.

Journal Article↗
PubMed2001

[Study on the interaction between Pd(II) and Rhus vernicifera laccase].

The influence of the mixing time of Pd(II) and Rhus vernicifera laccase on the oxidation of 5,6-dibromo-2,3-dicyanohydroquinone (DDBQH2) catalyzed by laccase has been studied through spectrophotometer at pH 4.5 and (30 +/- 0.1 degree C). The activation of Pd(II) on the laccase activity is gradually converted into inhibition and ultimately inactivation with the extension of the mixing time of Pd(II) and laccase, and the rate of such conversion goes up with the increase of Pd(II) concentration. The influence of Pd(II) on the absorption spectrum of laccase suggests that it is the type I site in laccase with which Pd(II) interacts and Pd(II) may gradually and at last substitute Cu(II) from the site. The substitution may be the cause of decrease and disappearance of laccase activity.

Binding Sites↗
PubMed2000

[Study on the interaction of Rhus vernicifera laccase with Hg2+ ion].

The influence of the mixed time of Hg2+ ion and Rhus vernicifera laccase on the oxidation of 5,6-dibromo-2,3-dicyanohydroquinone (DDBQH2) catalyzed by laccase has been studied at pH 4.4 and 30 +/- 0.2 degrees C. Hg2+ ion can activate the catalytic activity of laccase when the mixed time is short. With the extension of the mixed time, the activation is gradually converted into inhibition. The influence of Hg2+ ion on the absorption spectrum of laccase suggests that it may be the substitution that Hg2+ ion displaces Cu(II) from the type 1 site in laccase causing the inhibition of laccase activity.

English Abstract↗