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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↗

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↗

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↗

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↗

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↗

PubMedDate not supplied

Metabolism of trans-stilbene in rabbits and rats.

The biotransformation of intramuscularly administered 14C-labeled trans-stilbene was investigated in both rabbits and rats. In rabbits radioactivity was excreted (78.8% in 17 days) almost exclusively in the urine. In rats, feces accounted for more than half of the total excretion (80.3% in 19 days). Hydroxylated metabolites in urine and feces were identified by thin-layer chromatography and quantitated by liquid scintillation counting. They were 4-hydroxy and 4,4'-dihydroxystilbene, and the two monomethyl ethers of 3,4-dihydroxystilbene and 4,4'-dihydroxybibenzyl. In addition, four polyhydroxylated metabolites of stilbene and bibenzyl were identified in rat urine by comparison of gas-liquid chromatography retention times of their silyl derivatives with synthetic reference compounds. They were 3,4,4'-trihydroxystilbene, and 3,4-dihydroxy-, 3,4,4'=trihydroxy-, and 3,4,3',4'-tetrahydroxybibenzyl. Oxidative cleavage of trans-stilbene to benzoic acid and 4-hydroxy- and 3,4-dihydroxybenzoic acid was established by the presence of both the free acids and conjugates of these compounds in both rabbit and rat urine. Their glycine conjugates were identified by thin-layer chromatography and quantitated by reverse isotope dilution procedures from unhydrolyzed rabbit and rat urine. Percentages obtained indicate that cleavage of trans-stilbene is more extensive in rabbits (9.5%) than in rats (2.7%).

Animals↗

PubMed1992

Stilbene synthase from Scots pine (Pinus sylvestris).

Stilbene synthases are named according to their substrate preferences. By this definition, enzymes preferring cinnamoyl-CoA are pinosylvin synthases, and proteins with a preference for phenylpropionyl-CoA are dihydropinosylvin synthases. We investigated the assignment of a stilbene synthase cloned from Scots pine (Pinus sylvestris) as dihydropinosylvin synthase and the proposal of an additional pinosylvin synthase [1992, Plant Mol. Biol. 18, 489-503]. The results show that the previous interpretation was misled by several unexpected factors. Firstly, we found that the substrate preference and the activity of the plant-specific protein expressed in E. coli was influenced by bacterial factors. This was reduced by improvement of the expression system, and the subsequent kinetic analysis revealed that cinnamoyl-CoA rather than phenylpropionyl-CoA is the preferred substrate of the cloned stilbene synthase. Secondly, mixing experiments showed that extracts from P. sylvestris contain factor(s) which selectively influenced the substrate preference, i.e. the activity was reduced with phenylpropionyl-CoA, but not with cinnamoyl-CoA. This explained the apparent differences between plant extracts and the cloned enzyme expressed in E. coli. Taken together, the results indicate that the cloned enzyme is a pinosylvin synthase, and there is no evidence for a second stilbene synthase. This study cautions that factors in the natural and in new hosts may complicate the functional identification of cloned sequences.

Acyl Coenzyme A↗

PubMed1992

Pine stilbene synthase cDNA, a tool for probing environmental stress.

Stilbene synthase cDNAs were isolated from a pine (Pinus sylvestris) cDNA library. Poly(A)+RNA required for the preparation was obtained from young seedlings challenged with Botrytis cinerea. A full-length cDNA encoding pinosylvin-forming stilbene synthase was sequenced, and the deduced amino acid sequence was compared with sequences of resveratrol-forming stilbene synthases. The cDNA coding for the key enzyme of pinosylvin formation is a valuable tool for detecting early effects of environmental stress in pine needles.

Acyltransferases↗

PubMed1979

Acriflavine-Feulgen stilbene staining: a procedure for automated cervical cytology with a television based system (LEYTAS).

A sample preparation and staining procedure for automated cytology with a TV based system (LEYTAS) is described. It consists of a centrifugation technique and automated acriflavine-Feulgen stilbene staining of cervical specimens. The advantages of using both the fluorescence and the absorption image of acriflavine-Feulgen stilbene stained cervical cells for a television based system are discussed.

Acriflavine↗

PubMed1977

Epoxidation of the stilbene double bond, a major pathway in aminostilbene metabolism.

1. The vicinal diol 1-(4-acetylamino)-phenyl-2-phenyl-1,2-ethanediol is shown to be a major metabolite of cis- and trans-4-dimethylaminostilbene in the rat. 2. The threo-diastereomeric diols were identified in urine with both the cis- and trans-aminostilbene. This is consistent with enzymic trans-opening of an epoxide intermediate only for the cis-stilbene. For the hydrolysis of the trans-stilbene epoxide alternative mechanisms are discussed. 3. A mercapturic acid isolated from urine is identical with the reaction product of 4-acetylaminostilbene epoxide and N-acetylcysteine. This provides additional evidence for an epoxide intermediate. 4. Oxidation of the intercyclic linkage occurs also in 4-dimethylaminobibenzyl, leading to 1-phenyl-2-(4-acetylamino)-phenyl-1-ethanol as a major urinary metabolite. 5. The syntheses of several reference compounds, including the epoxides and dihydrodiols of cis- and trans-4-acetylaminostilbene are described.

Animals↗

PubMed1978

Stilbene synthases and stilbenecarboxylate synthases, I Enzymatic synthesis of 3,5,4-trihydroxystilbene from p-coumaroyl coenzyme A and malonyl coenzyme A.

1) Cell-free extracts prepared via acetone powder from rhizome of Rheum rhaponticum were found to be capable of converting p-coumaroyl-CoA and [2-14C]malonyl-CoA into a 3,5,4'-trihydroxystilbene, resveratrol. The product was characterized by repeated chromatography and by recrystallization to constant specific radioactivity. 2) The mode of condensation of the phenylpropanoid moiety with C2 units was determined by chemical degradation of the enzymatically formed product. 3) The enzyme system which catalyses the condensation of p-coumaroyl moiety with 3 malonyl units, the intramolecular aldol reaction and the subsequent decarboxylation was classified as stilbene synthase. It could be activated by dithiothreitol. 4) When the extraction of the rhizome was performed with aqueous grinding medium, a high percentage of this stilbene synthase activity was found to be membrane-bound.

Catalysis↗

PubMed1976

Inhibition of sulfate transport in Ehrlich ascites tumor cells by 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid(SITS).

The effects of the nonpenetrating amino reactive reagnet 4-acetamido-4'-isothiocyano-stilbene-2-2'-dilsulfonic acid (SITS) on anion transport (sulfate, chloride, and inorganic phosphate) were investigated in Ehrlich ascites tumor cells. Short time exposure to SITS produces a reversible inhibition (92%) of sulfate transport. The kinetics of interaction suggest that reversibly bound SITS competitively inhibits sulfate transport, Ki = 3 X 10(-6)M. Incubation of tumor cells with SITS (1 X 10(-4)M) for longer periods of time results in a time dependent irreversible inhibition of sulfate transport which obeys first order kinetics. The rate coefficient for the inactivation process is 0.040 min-1. The kinetics of irreversible inhibition is best explained by the irreversible binding of SITS to the sulfate transport site, and therefore makes SITS a potentially useful probe for the quantiation of these sites in the tumor cell. The lack of effect of irreversibly bound SITS on either chloride or inorganic phosphate transport points to a specificity in the interaction of SITS with the tumor cell membrane, as well as indicating that an alternate pathway exists for the movement of these anions across the membrane.

Biological Transport, Active↗

PubMed1975

Synthesis of clyclopropyl analogs of stilbene and stilbenediol as possible antiestrogens.

Conformationally rigid analogs of stilbene and stilbenediol were prepared via gem-dichlorocyclopropyl precursors utilizing two different synthetic methods: a two-phase catalytic method and an organomercurial method. These precursors were reduced to the corresponding cyclopropyl analogs using sodium and methanol. All compounds are being tested to discriminate between estrogenic and antiestrogenic ability, to determine estrogen binding ability, and to evaluate tissue culture anticancer activity.

Catalysis↗

PubMed1978

Inhibitory effects of 4,4'-diisothiocyano stilbene-2,2'-disulfonic acid (DIDS) in the response of isolated hepatocytes to phalloidin.

4,4'-Diisothiocyano stilbene-2,2'-disulfonic acid (DIDS) inhibits the typical development of protrusions, regularly seen after treatment of isolated hepatocytes with phalloidin. The degree of inhibition depends on the time of preincubation and on the concentration of DIDS, but not on the concentration of phalloidin. DIDS is more effective than H2DIDS. The inhibition by both compounds is irreversible. The binding capacity of hepatocytes for H2DIDS is much higher than that of the phalloidin-insensitive hepatoma cells. Gel electrophoresis of lysates from cells, pretreated with 3H2DIDS demonstrates that actin binds very little of the inhibitor. Our results suggest that a protein structure on the surface of hepatocytes, needed for the response to phalloidin, is influenced by DIDS or H2DIDS.

Animals↗

PubMed1976

A study of the relationship between inhibition of anion exchange and binding to the red blood cell membrane of 4,4'-diisothiocyano stilbene-2,2'-disulfonic acid (DIDS) and its dihydro derivative (H2DIDS).

DIDS (4,4'-diisothiocyano stilbene-2,2'-disulfonic acid) and H2DIDS (4,4'-diisothiocyano-1,2-diphenyl ethane-2,2'-disulfonic acid) binding to the human red cell membrane proteins were studied as a function of concentration, temperature and time. Most binding sites were common to both. The common sites were in band 3 of SDS polyacrylamide gel electropherograms (Steck, 1974. J. Cell Biol. 62:1), an unidentified adjacent band, and glycophorin. Reversible and irreversible binding occurred; both inhibited sulfate equilibrium exchange. The time courses of irreversible binding to band 3 and total binding to the membrane as a whole were biphasic. About 20% of H2DIDS and greater 60% of DIDS binding were rapid, independent of temperature. Slow H2-DIDS binding was monoexponential, activation enthalpy 23 kcal/mole. The stoichiometry of irreversible H2DIDS binding to band 3 was 1.1-1.2, concentration-dependent. Under the conditions studied (0-50 muM, hematocrit 10%, 5-37 degrees C) binding to band 3 was a constant fraction of total binding, 0.7 for H2DIDS and 0.8 for DIDS. Inhibition was a linear function of total binding, binding to band 3, and therefore also to nonband 3 sites, with either inhibitor during both phases, H2DIDS inhibition was complete at 1.9 X 10(6) or 1.2 X 10(6) molecules/cell total and band 3 binding respectively. For DIDS the corresponding figures were 1.3 X 10(6) and 1.1 X 10(6). It is shown how reagents of mixed function can react with biphasic kinetics. Binding to multiple contiguous sites may exhibit concentration-dependent stoichiometry. Under such conditions a linear inhibition-binding relationship is neither a necessary nor a sufficient condition for the identification of transport sites.

Benzenesulfonates↗

PubMed1979

Pathways for bicarbonate transfer across the serosal membrane of turtle urinary bladder: studies with a disulfonic stilbene.

Bicarbonate is transferred across the serosal (S) membrane of the epithelial cells of the turtle bladder in two directions. Cellular HCO3- generated behind the H+ pump moves this membrane into the serosal solution. This efflux of HCO3- is inhibited by SITS (4-isothiocyano-4'-acetamido-2,2'-disulfonic stilbene). When HCO3- is added to the serosal solution it is transported across the epithelium in exchange for absorbed Cl-. This secretory HCO3- flow traverses the serosal cell membrane in the opposite direction. In this study the effects of serosal addition of 5 x 10(-4) M SITS on HCO3- secretion and Cl- absorption were examined. The rate of H+ secretion was brought to zero by an opposing pH gradient, and 20 mM HCO3- was added to S. HCO3- secretion, measured by pH stat titration, was equivalent to the increase in M leads to S Cl- flux after HCO3- addition. Neither the S leads to M flux of HCO3- nor the M leads to S flux of Cl- were affected by SITS. In the absence of electrochemical gradients, net Cl- absorption was observed only in the presence of HCO3- in the media; under such conditions, unidirectional and net fluxes of Cl- were not altered by serosal or mucosal SITS. H+ secretion, however, measured simultaneously as the short-circuit current in ouabain-treated bladders decreased markedly after serosal SITS. The inhibition of the efflux of HCO3- in series with the H+ pump and the failure of SITS to affect HCO3- secretion and Cl- absorption suggest that the epithelium contains at least two types of transport systems for bicarbonate in the serosal membrane.

Animals↗