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At least 19 recordsLinked to original sources

PubMed1991

Coordinate- and elicitor-dependent expression of stilbene synthase and phenylalanine ammonia-lyase genes in Vitis cv. Optima.

The mechanisms controlling the induction of stilbene synthase and phenylalanine ammonia-lyase (PAL), two putative key regulatory enzymes of the biosynthetic pathway to stilbene phytoalexins, have been investigated. The induction was studied in cell suspension cultures of grape (Vitis cv. Optima) by treatment with fungal cell wall. Several independent cDNA clones for PAL and stilbene synthase were isolated from a cDNA library of fungal cell wall-induced grape cells and identified by sequence analysis. The stilbene synthase cDNA sequence of pSV21 predicted a protein of 392 amino acids and Mr 42,791, similar in size to that observed experimentally for immunodetected stilbene synthase. The cDNA sequences of pSV21 and pSV25 differed in 76 bp in the coding region. The sequences of grape stilbene synthase cDNAs exhibited significant homology to the sequence reported for the peanut stilbene synthase cDNA. Both PAL and stilbene synthase mRNA, measured by RNA blot hybridizations, were induced within 1 h of addition of fungal cell wall preparations to the cell cultures, rose to a maximum by the sixth hour, then declined slowly over the next 20 h. The activities of PAL and stilbene synthase were also induced in parallel, but reached their maximum at different times after fungal cell wall addition to the cell cultures. The induction patterns of stilbene synthase and PAL in grape and peanut are discussed.

Acyltransferases↗

PubMed1987

Purification of microsomal epoxide hydrolase from liver of rhesus monkey: partial separation of cis- and trans-stilbene oxide hydrolase.

Solubilized rhesus monkey liver microsomes were used as the starting material for the purification of epoxide (cis-stilbene oxide) hydrolase. Successive chromatography over DEAE-Sephacel followed by CM-cellulose resulted in two peaks of activity, CM A and CM B. Passage of these two eluates over separate hydroxyapatite columns resulted in two peaks of activity from CM A, HA A1, and HA A2, and one peak from CM B and HA B, with respective recoveries of 1, 7, and 0.2% of cis-stilbene oxide hydrolase activities. A similar recovery was found for benzo[a]pyrene-4,5-oxide hydrolase, while trans-stilbene oxide hydrolase activity coeluted only in HA A2. Fraction HA A1 was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoblots of the three eluates and solubilized microsomes incubated with anti-HA A1 demonstrated a single band at 49 kDa in each fraction. The three eluates were differentially affected by the inhibitors of epoxide hydrolase, trichloropropene oxide and 4-phenylchalcone oxide, and addition of Lubrol PX and phospholipid. Immunoprecipitation of HA A2 resulted in coprecipitation of cis- and trans-stilbene oxide hydrolase activity. Upon immunoprecipitation of solubilized microsomes, all the cis-stilbene oxide and benzo[a]pyrene-4,5-oxide, but only 50-60% of trans-stilbene oxide hydrolase activity was precipitated. These studies support findings with other species that (i) an immunochemically distinct cytosolic-like epoxide hydrolase exists in microsomes, and (ii) microsomal epoxide hydrolase activity can be separated during ion-exchange chromatography giving proteins with similar molecular weights and immunochemical cross-reactivity. The precipitation of cis- and trans-stilbene oxide hydrolase activity in eluate HA A2 provides convincing evidence that these isozymes are not structurally identical.

Animals↗

PubMed1992

A single change of histidine to glutamine alters the substrate preference of a stilbene synthase.

Stilbene and chalcone synthases are related polyketide synthases which use the same substrates but form different products. The environment of the condensing active site cysteine is highly conserved, except for the positions -2 and -3. All chalcone synthases contain Gln-Gln and prefer 4-coumaroyl-CoA as starter CoA ester, while the two known stilbene synthases contain Gln-His or His-Gln (preference phenylpropionyl-CoA and 4-coumaroyl-CoA, respectively). We investigated whether the presence and/or position of the histidine influences the substrate preference and the product specificity (stilbene or chalcone). The two amino acid motifs in the chalcone synthase from Pinus sylvestris (Gln-Gln) and in the stilbene synthases from P. sylvestris (Gln-His) and Arachis hypogaea (His-Gln) were changed by site-directed mutagenesis into all sequence combinations as found in the natural enzymes. Assays with the mutant proteins showed that the histidine does not determine the product specificity. With the chalcone and the stilbene synthase from P. sylvestris, any sequence deviation reduced the activity without marked effects on the substrate preference. The stilbene synthase from A. hypogaea was different. The change from His-Gln to Gln-His abolished enzyme activity almost completely with all three substrates. The change to Gln-Gln selectively reduced the activity with 4-coumaroyl-CoA, and the kinetic analysis indicated a slight increase in Km and a 3-fold reduction of Vmax, when compared with the parent enzyme. This converted the enzyme from a resveratrol-forming into a dihydropinosylvin-forming stilbene synthase.

Acyltransferases↗

PubMedDate not supplied

Simulation of the hepatic metabolism of stilbene and its tricyclic derivatives by Fenton and Ruff reagents: models for cytochrome P-450 activation of chemical carcinogens.

Reactions of trans-stilbene, cis-stilbene, 5H-dibenzo [a,d] cyclo-heptene 5-one and 5H-dibenz [b,f] azepine (iminostilbene) with Fenton reagent [Fe (II)/H2O2] clearly simulate their hepatic metabolism. Expoxidation on the corresponding ethylenic linkage was found to be a common pathway of these compounds. Epoxides of trans-stilbene, cis-stilbene, and 5H-dibenzo[a,d]cycloheptene 5-one were further oxidized to dihydrodiols, alpha-hydroxyketones, diketones, and finally cleavage of the ethylenic bonds to the formation of the corresponding aldehydes. However, the unstable epoxide of iminostilbene gave 9-acridinecarbaldehyde that is further oxidized to 9-acridone. Reaction of both trans- and cis-stilbene with Ruff reagent [Fe III)/H2O2] gave the same oxidative products to that obtained from Fenton reagent. The radical scavenger 2,6 bis (1,1-dimethylethyl)-4-methyl phenol (BHT) decreases the total yield conversion and increases the formation ratio of both cis-epoxide and d,l-hydrobenzoin from cis-stilbene.

Biotransformation↗

PubMed1990

Expression of a stilbene synthase gene in Nicotiana tabacum results in synthesis of the phytoalexin resveratrol.

A gene from groundnut (Arachis hypogaea) coding for stilbene synthase was transferred together with a chimaeric kanamycin resistance gene. It was found to be rapidly expressed after induction with UV light and elicitor in tobacco cells (Nicotiana tabacum). Comparative studies of stilbene synthase mRNA synthesis in groundnut and transgenic tobacco suspension cultures revealed the same kinetics of gene expression. Stilbene synthase specific mRNA was detectable 30 minutes after elicitor induction and 10 minutes after UV irradiation. The maximum of mRNA accumulation was between 2 and 8 hours post induction. 24 hours after induction stilbene synthase mRNA accumulation ceased. Furthermore, in transgenic tobacco plants, the gene was found to be inducible in sterile roots, stems and leaves. Stilbene synthase was demonstrated in crude protein extracts from transgenic tobacco cell cultures using specific antibodies. Resveratrol, the product of stilbene synthase, was identified by HPLC and antisera raised against resveratrol.

Acyltransferases↗

PubMed1987

Oxene transfer, electron abstraction, and cooxidation in the epoxidation of stilbene and 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene by hemoglobin.

Hemoglobin plus H2O2 oxidizes trans-stilbene to trans-stilbene oxide, cis-stilbene to cis- and trans-stilbene oxide, and trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene to anti-trans-7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene. Oxidation of cis- and trans-stilbene to the corresponding cis- and trans-epoxides proceeds exclusively with incorporation of oxygen from the peroxide. Oxidation of cis-stilbene to the trans-epoxide, however, proceeds without detectable incorporation of oxygen from the peroxide and partial incorporation of oxygen from O2. The epoxidations in which stereochemistry is conserved thus appear to involve ferryl oxygen transfer, whereas the epoxidations in which stereochemistry is inverted are proposed to involve protein-mediated cooxidation [Ortiz de Montellano, P.R., & Catalano, C.E. (1985) J. Biol. Chem. 260, 9265-9271] and possibly electron abstraction-water addition. The epoxidation of trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene incorporates oxygen from H2O2 and H2O but not O2. The oxidation of this substrate is thus consistent with ferryl oxygen transfer and electron abstraction but not protein-mediated cooxidation.

Animals↗

PubMed1989

Lysine 539 of human band 3 is not essential for ion transport or inhibition by stilbene disulfonates.

The anion transporter from human red blood cells, band 3, has been expressed in Xenopus laevis frog oocytes microinjected with mRNA prepared from the cDNA clone. About 10% of the protein is present at the plasma membrane as determined by immunoprecipitation of covalently bound 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS) with anti-DIDS antibody. The expressed band 3 transport chloride at a rate comparable to that in erythrocytes. Transport of chloride is inhibited by stilbene disulfonates, niflumic acid, and dipyridamole at concentrations similar to those that inhibit transport in red blood cells: DIDS and 4,4'-dinitro-2,2'-stilbene disulfonate inhibit chloride uptake with Kiapp of 34 nM and 2.5 microM, respectively. Lysine 539 has been tentatively identified as the site of stilbene disulfonate binding. Site-directed mutagenesis of this lysine to five different amino acids has no effect on transport. Inhibition by stilbene disulfonates or their covalent binding was not affected when Lys-539 was substituted by Gln, Pro, Leu, or His. However, substitution by Ala resulted in weaker inhibition and covalent binding. These results indicate that lysine 539 is not part of the anion transport site and that it is not essential for stilbene disulfonate binding and inhibition.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1978

The effect of a disulfonic acid stilbene on proximal cell membrane potential in Necturus kidney.

The effects of 0.5 mM 4-acetamido-4'-isothiocyano-stilbene-2,2' disulfonic acid on the electrical properties of the peritubular membrane were studied in the proximal tubule of the perfused Necturus kidney. The addition of stilbene isothiocyanate disulfonic acid in peritubular perfusate resulted in an average 4.5 mV hyperpolarization with no detectable changes of peritubular membrane input conductance. The depolarization elicited by high-K media was enhanced by 18% in the presence of stilbene isothiocyanate disulfonic acid, an observation indicating that the inhibitor increased the contribution of potassium to membrane potential, presumably by decreasing anionic permeabilities. The hyperpolarizing effect of stilbene isothiocyanate disulfonic acid was abolished when peritubular bicarbonate was removed from the medium and isoosmotically replaced by chloride. These data suggest that (a) intracellular bicarbonate activity is higher than that predicted from passive distribution, (b) stilbene isothiocyanate disulfonic acid decreases P HCO3, thus hyperpolarizing the membrane, (c) chloride distribution appears to be passive when bicarbonate is removed from the peritubular perfusate. The state of Cl distribution when extracellular bicarbonate is at physiologic concentration cannot be assessed from the present data.

Animals↗

PubMed1992

An alternative pathway of B cell activation: stilbene disulfonates interact with a Cl- binding motif on AEn-related proteins to stimulate mitogenesis.

Stilbene disulfonates are known to competitively inhibit Cl-/HCO3- flux through Band 3-related anion exchange (AE) proteins. To study the role of AE in lymphocyte activation, stilbene disulfonates were added to cultures of rat splenocytes (SPL). Four different stilbene derivatives were tested and each directly stimulated mitogenic proliferative responses of SPL. The mitogenic activity of these analogs paralleled their known patterns of interaction with Band 3-related AE proteins, as measured by; (a) their effective mitogenic concentrations, (b) their rank order of mitogenic potency [DIDS greater than SITS greater than DNDS congruent to DAzDS], (c) their patterns of nonreversible binding to the mitogenic receptor [DIDS much greater than SITS, DNDS], and (d) the specific, noncompetitive inhibition of their activity by the antagonist niflumic acid. Stilbene disulfonates directly activated purified B cell populations but not isolated T cells and furthermore, acted in synergy with anti-IgM to stimulate proliferation of SPL. These findings show that stilbene disulfonates represent a novel class of mitogens that interact with AEn-related proteins to stimulate an alternative activation pathway in B cells. These studies also indicate that immunomodulating activities of nonsteroidal anti-inflammatory drugs such as niflumic acid may be mediated, in part, by their interactions with AEn-related proteins.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1987

Renal basolateral membrane anion transporter characterized by a fluorescent disulfonic stilbene.

The fluorescence enhancement of 4,4'-dibenzamido-2,2'-disulfonic stilbene (DBDS) upon binding to membranes was used to examine proximal tubule stilbene binding sites. Equilibrium binding studies of DBDS to renal brush border (BBMV) and basolateral membrane vesicles (BLMV) were performed using a fluorescence enhancement technique developed for red blood cells (A.S. Verkman, J.A. Dix and A.K. Solomon, J. Gen. Physiol. 81:421-449, 1983). In the absence of transportable anions, DBDS bound reversibly to a single class of sites on BLMV isolated from rabbit (Kd = 3.8 microM) and rat (3.2 microM); 100 microM dihydro-4,4'-diisothiocyano-2,2'-disulfonic stilbene (H2DIDS) blocked greater than 95% of binding. H2DIDS inhibitable DBDS binding was not detected using rat or rabbit BBMV. In rabbit BLMV, DBDS Kd doubled with 10 mM SO4, 50 mM HCO3 and 100 mM Cl, but was not altered by Na or pH (6-8). In stopped-flow experiments the exponential time constant for DBDS binding slowed with SO4, HCO3 and Cl, but was unaffected by Na. These results are consistent with competitive binding of DBDS and anions at an anion transport site. To relate DBDS binding data to anion transport inhibition we used 35SO4 uptake to characterize several modes of rabbit BLM anion transport: H/SO4 and Na/SO4 cotransport, and Cl/SO4 countertransport. Each transport process was electroneutral and was inhibited by H2DIDS, furosemide, probenecid, chlorothiazide and DBDS. The apparent KI's for DBDS (3-20 microM) were similar to Kd for DBDS binding. These studies define a class of anion transport sites on the proximal tubule basolateral membrane measurable optically by a fluorescent stilbene.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

PubMed1976

Effects of 4-acetamido-4'-isothiocyano-2,2-disulfonic stilbene on ion transport in turtle bladders.

The disulfonic stilbene (4-acetamido-4'-isothiocyano-2,2'-disulfonic stilbene) is found to be more potent than acetazolamide as an anion transport inhibitor in the turtle bladder, but less potent than acetazolamide as a carbonic anhydrase inhibitor. The anion-dependent (HCO-3,Cl-) moiety of the short-circuiting current is eliminated by 4-acetamido-4'-isothiocyano-2,2'-disulfonic stilbene, but only after its addition to the serosal bathing fluid. Whereas 4-acetamido-4'-isothiocyano-2,2'-disulfonic stilbene has no effect on Na+ transport across the bladder, it is more potent than ouabain as an inhibitor of microsomal (Na+ + K+)-ATPase of both turtle bladder and eel electric organ.

Acetazolamide↗

PubMed1978

trans-Stilbene oxide: an inducer of rat hepatic microsomal and nuclear epoxide hydrase and mixed-function oxidase activities.

The administration of trans-stilbene oxide to rats resulted in increased hepatic microsomal and nuclear epoxide hydrase (with styrene oxide (SO), benzo[a]pyrene 4,5-oxide (4,5-BP) as substrates) and aryl hydrocarbon hydroxylase (AHH) activities. Hepatic microsomal aminopyrine N-demethylase, benzphetamine N-demethylase, and ethylmorphine N-demethylase activities were also increased. These increases in microsomal enzyme activity were dose- and time-dependent (about 100% at 200 mg/kg body weight, administered for 2 consecutive days). However, only marginal increases in hepatic microsomal NADPH-cytochrome c reductase activity and cytochrome P-450 content were observed. No apparent proliferation of hepatic endoplasmic reticulum occurred in trans-stilbene oxide pretreated rats. The administration of trans-stilbene oxide has no effect on hepatic glutathione S-transferase activities (with SO or 4,5-BPO as substrates). None of the parameters were affected in pulmonary microsomes from treated rats. The in vitro addition of trans-stilbene oxide (10(-6)--10(-2) M) did not affect hepatic epoxide hydrase or glutathione S-transferase activities.

Animals↗

PubMed1990

Grapevine stilbene synthase cDNA only slightly differing from chalcone synthase cDNA is expressed in Escherichia coli into a catalytically active enzyme.

Stilbene synthase is responsible for the formation of resveratrol and other stilbenes which function in grapevine as phytoalexins. A full-length stilbene synthase cDNA was prepared from grapevine mRNA and sequenced. The insert in pSV25 coding for a polypeptide with 392 amino acids was inserted into the vectors pKK233-2 and pDS12/RBSII-2, respectively. Expression of the cDNA in Escherichia coli yielded an enzymatically active dimer exhibiting solely stilbene synthase activity. The protein was characterized by enzyme activity and Western blot analysis.

Acyltransferases↗

PubMed1991

Comparative studies of the effects of stilbene compounds on hepatic ornithine decarboxylase and S-adenosylmethionine decarboxylase induction in rats.

Trans-Stilbene oxide (TSO, 2 mmol/kg, ip.) induced ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) to 60-fold and 5-fold of the controls, respectively, in the liver of rats. Parallel to ODC induction, there was a marked increase in putrescine content to 50-fold of the control levels. Cis-Stilbene oxide (CSO), a stereoisomer of TSO, also produced the induction of ODC and SAMDC and the increase in putrescine content. There was no difference in the ability to induce ODC and SAMDC between TSO and CSO with respect to the extents of induction and the time needed to reach maximal levels. Trans-Stilbene (TS), a mother compound of TSO, did not show such an effect on ODC, while cis-stilbene (CS) induced both ODC and SAMDC. Treatment with glutathione inhibited TSO- and CSO-mediated induction of ODC and SAMDC. These findings add new information concerning the abilities of TSO, CSO and CS on hepatic polyamine metabolism.

Acetylcysteine↗

PubMed1992

Stilbene disulphonates inhibit apparently separate chloride transporters in skeletal muscle of Rana temporaria.

1. Inhibition of 36Cl- efflux in frog muscle by the stilbene disulphonates (SD) SITS (4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulphonate) and DNDS (4,4'-dinitro-stilbene-2,2'-disulphonate) depends on the external pH, while the blocking of Cl- conductance with SITS is independent of pH. The 36Cl- efflux inhibition with DNDS has been studied in thin depolarized muscle fibre bundles in order to examine whether this difference is consistent with one transporter or reflects the existence of two mutually independent conductive and non-conductive SD-sensitive Cl- pathways. 2. The 36Cl- efflux response to a sudden inward KCl gradient was studied. At high pH the efflux decreased as predicted for dominant conductive Cl- single-filing, and at low pH the efflux increased in agreement with dominant non-conductive Cl- antiport. DNDS inhibition resulted in the same response, an efflux decrease, at both high and low pH, suggesting a selective reduction of the non-conductive contribution at low pH. 3. The inhibition of 36Cl- efflux as a function of the DNDS concentration at an external pH of 6.9 showed complex kinetics, which could be described as the sum of two Michaelis-Menten functions with different half-inhibition concentrations of DNDS. 4. The results support the hypothesis that the stilbene disulphonate-sensitive Cl- transport is mediated by two separate transporters rather than one.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

PubMed1986

Target molecular weights for red cell band 3 stilbene and mercurial binding sites.

Radiation inactivation was used to measure the target sizes for binding of disulfonic stilbene anion transport inhibitor 4,4'-dibenzamido-2,2'-disulfonic stilbene (DBDS) and mercurial water transport inhibitor p-chloromercuribenzene sulfonate (pCMBS) to human erythrocytes. The measured target size for erythrocyte ghost acetylcholinesterase was 78 +/- 3 kDa. DBDS binding to ghost membranes was measured by a fluorescence enhancement technique. Radiation (0-26 Mrad) had no effect on total membrane protein and DBDS binding affinity, whereas DBDS binding stoichiometry decreased exponentially with radiation dose, giving a target size of 59 +/- 4 kDa. H2-4,4'-diisothiocyano-2,2'-disulfonic stilbene (H2-DIDS, 5 microM) blocked greater than 95% of DBDS binding at all radiation doses. pCMBS binding was measured from the time course of tryptophan fluorescence quenching in ghosts treated with the sulfhydryl reagent N-ethylmaleimide (NEM). Radiation did not affect the kinetics of tryptophan quenching, whereas the total amplitude of the fluorescence signal inactivated with radiation with a target size of 31 +/- 6 kDa. These results support the notion that DBDS and pCMBS bind to the transmembrane domain of erythrocyte band 3 in NEM-treated ghosts and demonstrate that radiation inactivation may probe a target significantly smaller than a covalently linked protein subunit. The small target size for the band 3 stilbene binding site may correspond to the intramembrane domain of the band 3 monomer (52 kDa), which is physically distinct from the cytoplasmic domain (42 kDa).

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

PubMed1990

Fluorescent stilbene (BADS) binding proteins in anion-transporting epithelia.

Chloride transport occurs at the interface between the internal and external environments of a cell where chloride uptake or efflux is regulated through a variety of mechanisms that involve cotransport of cations, exchange mechanism with anions, or movement through channels. One of these mechanisms, a chloride-bicarbonate exchange found in the human red blood cell, is well characterized and is mediated by a protein commonly known as band 3. To ascertain the presence of this or other mechanisms in epithelia, the sensitivity of epithelial membranes toward stilbenes was examined. Structure function activities of stilbene derivatives with red cell ghosts show that stilbene molecules block anion transport sites. One of these stilbenes, 4-benzamido-4'-aminostilbene-2-2'-disulfonic acid (BADS), chosen for its property of enhanced fluorescence on binding to hydrophobic sites, was used as a probe to examine the presence or absence of similar sites on epithelial membranes. With the use of nonlinear curve fitting, a single class of sites was found for BADS in the rat kidney cortex (1.6 microM), rat kidney medulla (2.1 microM), rat small intestine (2.2 microM), rat pancreatic islets (5.8 microM), frog cornea (4.3 microM), and shark rectal gland (1.5 microM). In the presence of chloride, the affinity for BADS decreased in all tissues except the frog corneal epithelium where it remained unchanged. The binding of BADS could be displaced by loop diuretics (furosemide, bumetanide, and piretanide) and thiocyanate anion in the kidney, intestine, and shark rectal gland; 50% displacement occurred at approximately 40 microM concentrations for furosemide with an order of magnitude less for bumetanide. The near-millimolar concentrations required for the displacement of BADS by loop diuretics indicate that this effect is nonspecific. However, the effect of chloride, thiocyanate, and loop diuretics on the binding of BADS indicates that BADS possibly interacts with an anion site.

Animals↗

PubMed1989

Characterization of semiquinone free radicals formed from stilbene catechol estrogens. An ESR spin stabilization and spin trapping study.

Electron spin resonance spectroscopy has been used to detect, characterize, and to infer structures of o-semiquinones derived from stilbene catechol estrogens. Radicals were generated enzymatically using tyrosinase and were detected as their Mg2+ complexes. It is suggested that initial hydroxylation of stilbene estrogen gives a catechol estrogen in situ; subsequent two-electron oxidation of the catechol to the quinone, followed by reverse disproportionation, leads to the formation of radicals. Consistent with this mechanism, o-phenylenediamine, a quinone trapping agent, inhibits formation of o-semiquinones. A competing mechanism of radical production involves autoxidation of the catechol. Hydroxyl radicals are shown to be produced in this system via a mechanism involving reduction of iron and copper complexes by stilbene catechols. Possible differences in the reactivity of stilbene ortho- and para-semiquinones are discussed.

Benzoquinones↗