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PubMed1975

Catalysis of phosphoryl group transfer. The role of divalent metal ions in the hydrolysis of lactic acid O-phenyl phosphate and salicylic acid O-aryl phosphates.

The spontaneous hydrolyses of lactic acid O-phenyl phosphate (I) and, to a lesser extent, 3-hydroxybutyric acid O-phenyl phosphate (II) have been investigated and compared with similar intramolecular and bimolecular reactions. Compared to bimolecular nucleophilic reactions, the reactivity of II is similar to other systems involving the formation of a six-membered ring intermediate, which suggests that the electrostatic barrier to attack of an anionic nucleophile on a phosphate diester anion is fully present in II. The reactivity of I, as compared to that of II, would suggest that at least a partial overcoming of the electrostatic barrier takes place upon closer approimation of the two reacting centers. The Mn-2+-catalyzed hydrolysis of I exhibits saturation kinetics, consistent with the enhanced reactivity of the metal ion-substrate complex. The binding constant for this complex, determined from kinetics, is in good agreement with that obtained by electron spin resonance (ESR) titration. It is argued that the complex of Mn-2+ with II, as observed by pulsed Fourier transform nuclear magnetic resonance (NMR) techniques, is a precursor to the complex of catalytic significance. The hydrolysis of I as catalyzed by a variety of divalent metal ions suggests an optimal metal ion size. The spontaneous and metal ion catalyzed hydrolyses of salicyclic acid O-aryl phosphates (IIIa-d) proceed through cyclic acyl phosphate intermediates after expulsion of phenol. Product studies on the parent compound have failed to detect phenyl phosphate as a product in either the spontaneous or metal ion catalyzed process. The dependence of the second-order rate constant for the metal-catalyzed hydrolysis on leaving group pKa, beta-1-g, decreases significantly relative to beta-1-g for the spontaneous hydrolysis. From the collective data a specific interation of the metal ion with a pentacovalent intermediate is inferred in the rate-determining step for esters I and III. The probable consequences of these mechanistic postulates for phosphoryl transfer reactions in biological systems are discussed.

Cations, Divalent↗
PubMed1986

Prostaglandin synthesis by rat uterine homogenates in the presence of copper ions, and the effects of indomethacin and salicylic acid.

While no significant effects on the in vitro production of PGF2 alpha by homogenates of rat estrous uteri were observed in the presence of 10(-3) and 10(-6) M Cu2+, the presence of Cu2+ at 10(-4) and 10(-5) M was found to stimulate production with maximal synthesis of PGF2 alpha occurring with 10(-4) M Cu2+. By contrast, the synthesis of PGE2 and PGI2 (determined as 6-keto PGF1 alpha) were unaffected at all of the different Cu2+ concentration used. When indomethacin and salicylic acid were tested for their effects on the Cu2+-mediated levels of PG synthesis by the homogenates, indomethacin (at 20 microM) was found to cause similar pronounced decreases in PGF2 alpha, PGE2 and 6-keto PGF1 alpha whereas salicylic acid (400 microM) showed preference towards suppressing PGE2 and 6-keto PGF1 alpha production.

Animals↗
PubMed1991

Comparative acute nephrotoxicity of salicylic acid, 2,3-dihydroxybenzoic acid, and 2,5-dihydroxybenzoic acid in young and middle aged Fischer 344 rats.

Experimental evidence suggests that the oxidative metabolites 2,3- and 2,5-dihydroxybenzoic acid (DIOH) may be responsible for the nephrotoxicity of salicylic acid (SAL). In the present study, enzymuria in conjunction with glucose (GLU) and protein (PRO) excretion were used as endpoints to compare the relative nephrotoxicity of SAL with 2,3- and 2,5-DIOH. In addition, the effect of age on enzymuria and GLU and PRO excretion following treatment with SAL or 2,3- and 2,5-DIOH was investigated because the elderly are at greater risk for SAL-induced nephrotoxicity. Three and 12-month male Fischer 344 rats were administered either no treatment, vehicle, SAL, 2,3-DIOH, or 2,5-DIOH at 500 mg/kg p.o. in 5 ml/kg corn oil/DMSO (5:1). Effects of these treatments on functional integrity of renal tissue was assessed from 0--72 h after dosing by measurement of urinary creatinine, GLU, and PRO, as well as excretion of proximal and distal tubular renal enzymes. Enzymes measured as indicators of proximal tubular damage were N-acetyl-beta-glucosaminidase (NAG), gamma glutamyltransferase (GGT), alanine aminotransferase (ALT), and alkaline phosphatase (AP), while urinary lactate dehydrogenase (LD) and aspartate aminotransferase (AST) were measured as indicators of distal tubular damage. In comparison to 3-month vehicle-treated rats, 2,3- and 2,5-DIOH caused a significant increase between 0-8 h in excretion of urinary GLU and activities of AST, NAG, and LD, with peak effects occurring between 4-8 h. Toxic effects of either metabolite were not evident beyond 24 h, and toxicity of 2,5-DIOH was significantly greater in comparison to 2,3-DIOH. SAL treatment resulted in similar effects on enzymuria as well as GLU and PRO excretion, but peak effects did not occur until 16-24 h, and often persisted until 72 h after dosing. Maximal enzymuria in response to SAL treatment was significantly greater in 12- vs. 3-month rats for AST, NAG, and LD. In response to 2,3-DIOH treatment, the maximal response was significantly greater in 12- vs. 3-month rats for LD and AST, and for NAG in response to 2,5-DIOH treatment. The results of this study suggest that both 2,3- and 2,5-DIOH are nephrotoxic metabolites of SAL, but implicate 2,5-DIOH as the more potent nephrotoxic metabolite. The relative lack of an age effect for 2,3- and 2,5-DIOH vs. SAL supports the hypothesis [2] that age-related differences in biotransformation of SAL, and not increased tissue sensitivity to 2,3- or 2,5-DIOH, contribute to the age-related increase in susceptibility to SAL-induced nephrotoxicity.

Acetylglucosaminidase↗
PubMed2003

Salicylic acid is an uncoupler and inhibitor of mitochondrial electron transport.

The effect of salicylic acid (SA) on respiration and mitochondrial function was examined in tobacco (Nicotiana tabacum) suspension cell cultures in the range of 0.01 to 5 mm. Cells rapidly accumulated SA up to 10-fold of the externally applied concentrations. At the lower concentrations, SA accumulation was transitory. When applied at 0.1 mm or less, SA stimulated respiration of whole cells and isolated mitochondria in the absence of added ADP, indicating uncoupling of respiration. However, at higher concentrations, respiration was severely inhibited. Measurements of ubiquinone redox poise in isolated mitochondria suggested that SA blocked electron flow from the substrate dehydrogenases to the ubiquinone pool. This inhibition could be at least partially reversed by re-isolating the mitochondria. Two active analogs of SA, benzoic acid and acetyl-SA, had the same effect as SA on isolated tobacco mitochondria, whereas the inactive p-hydroxybenzoic acid was without effect at the same concentration. SA induced an increase in Aox protein levels in cell suspensions, and this was correlated with an increase in Aox1 transcript abundance. However, when applied at 0.1 mM, this induction was transient and disappeared as SA levels in the cells declined. SA at 0.1 mM also increased the expression of other SA-responsive genes, and this induction was dependent on active mitochondria. The results indicate that SA is both an uncoupler and an inhibitor of mitochondrial electron transport and suggest that this underlies the induction of some genes by SA. The possible implications of this for the interpretation of SA action in plants are discussed.

Base Sequence↗
PubMed2004

Study of lanthanide complexes with salicylic acid by photoacoustic and fluorescence spectroscopy.

Solid complexes Ln(Sal)3.H2O (Sal: salicylic acid; Ln: La3+, Nd3+, Eu3+, Tb3+) are synthesized, and their photoacoustic (PA) spectra in the UV-Vis region have been recorded. PA intensities of central lanthanide ions are interpreted in terms of the probability of nonradiative transitions. It is found that PA intensity of the ligand increases in the order of Tb(Sal)3.H2O < La(Sal3).H2O < Eu(Sal)3.H2O < Nd(Sal)3.H2O. Different PA intensities of the ligand are interpreted by comparison with the fluorescence spectra. Ternary complexes Eu(Sal)3Phen and Tb(Sal)3Phen (Phen: 1,10-phenanthroline) are synthesized. Compared with their binary complexes, PA intensity of the ligand Sal decreases for Eu(Sal)3Phen, while the reverse is true for that of Tb(Sal)3Phen. The luminescence of Eu3+ increases remarkably when Phen is introduced, and luminescence of Tb3+ decreases greatly when Phen is added. The intramolecular energy transfer and relaxation processes in the complexes are discussed from two aspects: radiative and nonradiative relaxations.

Acoustics↗
PubMed1995

Developmentally related responses of maize catalase genes to salicylic acid.

The response of the maize catalase genes (Cat1, Cat2, and Cat3) to salicylic acid (SA) was examined at two distinct developmental stages: embryogenesis and germination. A unique, germination-related differential response of each maize catalase gene to various doses of SA was observed. During late embryogenesis, total catalase activity in scutella increased dramatically with 1 mM SA treatment. The accumulation of Cat2 transcript and CAT-2 isozyme protein provided the major contribution to the observed increase in total catalase activity. This increase was paralleled by the enhanced growth of germinated embryos at that stage. In a CAT-2 null mutant line, a full compensation of total catalase activity by the CAT-1 isozyme was observed in the presence of SA. This suggests that catalase is important for maintenance of normal cellular processes under stress conditions. SA at 1 mM, which enhances growth of precociously germinated embryos, appeared to inhibit seed germination at 1 day after inhibition. Furthermore, Cat2 transcript accumulation was inhibited at this stage. SA is probably not a direct signal for the induction of the catalase genes. Other signals, possibly germination-related regulator(s), might be responsible for the induction of the catalase genes. The effect of SA on the activity of purified catalase protein was also examined.

Catalase↗
PubMed1997

Salicylic acid induces changes in the physical properties of model and native kidney membranes.

Salicylic acid (SA) can inhibit the facilitated transport of inorganic sulfate in the kidney, placenta, and erythrocytes. One mechanism of this inhibition could involve the interaction of SA with membranes, resulting in altered function of transporter protein(s) due to changes in membrane fluidity. Such membrane effects could result in altered membrane transport and consequently in changes in the pharmacokinetics and the therapeutic activity of both xenobiotics and endogenous substrates. We investigated the effect of SA on the fluidity of brush border membrane (BBM) and basolateral membrane (BLM) isolated from rat kidney and also on the physical properties (such as phase transition temperature and fluidity) of model membranes by fluorescence polarization and differential scanning calorimetry (DSC) techniques. SA decreased the lipid order parameter (S) of BBM and BLM membranes in a concentration-dependent manner, indicating that the addition of SA makes the membrane more fluid. The fluidizing effect of SA was more pronounced than that of benzyl alcohol. Studies were carried out with protein-free model membranes composed of dipalmitoylphosphatidylcholine (DPPC) to investigate the effects of SA on the bilayer membrane lipids. SA decreased the fluorescence polarization of DPH (1,6-diphenyl 1,3,5-hexatriene) incorporated in DPPC vesicles. DSC studies demonstrated that SA broadened the phase transition temperature of DPPC vesicles and suggested that SA is located in the C1-C8 region of the acyl chain. In protein-free model membranes, SA exerted fluidizing effects through its incorporation into the cooperative hydrophobic region of the bilayer. The perturbation of membrane physical properties induced by SA and its hydrophobic localization in the membrane bilayer may be important in the SA-induced alteration of sulfate membrane transport.

Animals↗
PubMed1994

Salicylic acid, active oxygen species and systemic acquired resistance in plants.

Infection of plants, particularly by a necrotizing pathogen, usually induces a long-lasting, broad-based, systemic resistance to secondary pathogen attack. Many studies implicate salicylic acid as an essential signal in the development of such systemic acquired resistance in several plant species. Salicylic acid appears to mediate plant defence by binding to and inhibiting catalase, thus increasing the concentration of H(2)O(2) and other active oxygen species. Active oxygen species may then act as second messengers that induce plant defence gene expression, analogous to their activation of gene expression in mammalian cells.

Journal Article↗
PubMed2000

Induction of tcI 7, a gene encoding a beta-subunit of proteasome, in tobacco plants treated with elicitins, salicylic acid or hydrogen peroxide.

We previously isolated, by differential display and 5' RACE (rapid amplification of cDNA ends), cDNAs corresponding to genes activated following cryptogein treatment of tobacco cell suspensions, among them tcI 7 (tcI for tobacco cryptogein Induced), a gene encoding a beta-subunit of proteasome. Here, we report that tcl 7 was up-regulated in tobacco plants treated with elicitins (cryptogein and parasiticein) that have been shown to induce a systemic acquired resistance (SAR). Moreover, subsequent inoculation of tobacco with the pathogen Phytophthora parasitica var. nicotianae (Ppn) was shown to induce an additional activation of tcI 7 in tobacco plants pretreated with cryptogein. We also showed an up-regulation of tcI 7 by salicylic acid (SA). Moreover, accumulation of tcI 7 transcripts after treatment with cryptogein or with SA only occurred in NahG 9-tobacco plants that do not express the salicylate hydroxylase and thus are able to accumulate SA and develop a SAR. Suppressed accumulation of tcI 7 transcripts in NahG 8+ tobacco plants after cryptogein or SA treatment correlated with the loss of SAR. H2O2 was also shown to up-regulate tcI 7 in tobacco plants. Using gene walking by PCR we cloned and sequenced the 5' flanking region of tcI 7 containing hypothetical regulatory sequences, especially myb and NF-kappaB boxes, that could be responsible for the regulation of tcI 7 by salicylic acid and H2O2 respectively.

Amino Acid Sequence↗
PubMed2001

Molecular cloning and heterologous expression of novel glucosyltransferases from tobacco cultured cells that have broad substrate specificity and are induced by salicylic acid and auxin.

Scopoletin is one of the phytoalexins in tobacco. Cells of the T-13 cell line (Nicotiana tabacum L. Bright Yellow) accumulate a large amount of scopoletin, also known as 7-hydroxy-6-methoxycoumarin, as a glucoconjugate, scopolin, in vacuoles. We report here the molecular cloning of glucosyltransferases that can catalyze the glucosylation of many kinds of secondary metabolites including scopoletin. Two cDNAs encoding glucosyltransferase (NtGT1a and NtGT1b) were isolated from a cDNA library derived from the tobacco T-13 cell line by screening with heterologous cDNAs as a probe. The deduced amino-acid sequences of NtGT1a and NtGT1b exhibited 92% identity with each other, approximately 20-50% identities with other reported glucosyltransferases. Heterologous expression of these genes in Escherichia coli showed that the recombinant enzymes had glucosylation activity against both flavonoids and coumarins. They also strongly reacted with 2-naphthol as a substrate. These recombinant enzymes can utilize UDP-glucose as the sugar donor, but they can also utilize UDP-xylose as a weak donor. RNA blot analysis showed that these genes are induced by salicylic acid and auxin, but the time course of the expression was different. This result is similar to the changes in scopoletin glucosylation activity in these tobacco cells after addition of these plant growth regulators. These results might suggest that one of the roles of the products of these genes is scopoletin glucosylation, in response to salicylic acid and/or auxin, together with the other glucosyltransferases in tobacco cells.

Amino Acid Sequence↗
PubMed1977

Bioavailability of D-propoxyphene, acetyl salicylic acid, and phenazone in a combination tablet (Doleron): interindividual variation and influence of food intake.

The influence of food intake on the bioavailability of three analgesic compounds--propoxyphene chloride, acetyl salicylic acid and phenazone--in a combination tablet, Doleron, has been examined in eight healthy volunteers. A single oral dose was given both on an empty stomach and together with a standardized breakfast meal. The plasma concentrations of propoxyphene, its major metabolite norpropoxyphene, salicylic acid and phenazone were determined by mass fragmentography, spectrofluorimetry and gas chromatography. Concomitant food intake had no consistent influence on the bioavailability of any of the components. Hence, doleron may be taken together with meals as well as between meals. Large interindividual variations in propoxyphene and phenazone concentrations were found, indicating that an optimal effect will not always be obtained by standard doses.

Adult↗
PubMed2004

Salicylic acid alters endothelin-1 binding in intact adult rat ventricular myocytes.

Endothelin receptors ET(A)R and ET(B)R form tight receptor-ligand complexes that complicate our understanding of the physiological, pharmacological, and biochemical properties of these receptors. Although radioligand-binding studies have demonstrated the binding of endothelin-1 (ET-1) to ET(A)R to be essentially irreversible, ET(A)R internalize in a ligand-dependent manner, release ET-1, and then recycle to the cell surface. Salicylic acid (SA) reduces ET-1 binding (IC(50) = 10 mmol/L) to recombinant ET(A)R in isolated membranes by promoting dissociation of [(125)I]ET-1. In the present study, SA (5 mmol SA/L) did not alter [(125I)]ET-1 binding to intact adult rat ventricular myocytes. The lack of effect was not due to internalization of receptor-ligand complexes. However, 100 mmol SA/L significantly reduced [(125)I]ET-1 binding to both intact myocytes and isolated membranes. SA induced the phosphorylation p42/44 extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase and an unidentified 40-kDa protein on the activating threonine-glutamic acid-tyrosine (T-E-Y) motif. ERK phosphorylation was reduced by a MAP kinase kinase (MEK) inhibitor, PD98059. Phosphorylation of p40 was reduced by the p38 MAP kinase inhibitor SB203580, but not PD98059. However, inhibition of ERK or p38 MAP kinases did not alter the ability of 100 mmol SA/L to induce dissociation of [125I]ET-1. These results suggest that, in the ventricular myocyte, salicylic acid alters the kinetics of ET-1 binding. The results also suggest an allosteric binding site may be present that modulates the dissociation of ET-1 receptor-ligand complexes in response to an as-of-yet unidentified mediator.

Animals↗
PubMed1971

Influence of metal ions on the formation of mycobactin and salicylic acid in Mycobacterium smegmatis grown in static culture.

Mycobacterium smegmatis was grown on trace-metal-free medium in static culture. Throughout the growth phase, the concentration of mycobactin increased continuously, reaching a maximum of about 30 to 40 mug of mycobactin/mg of cell dry weight after 6 days; the concentration of salicylic acid remained approximately constant at 1 to 2 mug of salicylic acid/mug of cell dry weight. Fe(2+) (or Fe(3+)), Zn(2+), Mn(2+), and Mg(2+) were all essential to a maximum formation of mycobactin. Optimum concentrations required were: Fe(2+), about 1.8 mum; Mn(2+) and Zn(2+), about 0.5 mum; and Mg(2+), at least 0.17 mm. Higher levels of Fe(2+) (9 to 90 mum) and Zn(2+) (2 to 7 mum) repressed mycobactin to about half the maximum value. No other cation or anion apparently is required for mycobactin biosynthesis. Salicylic acid concentration increased about fourfold when iron was omitted from the medium, but this is not as great as the increase reported previously for this strain of M. smegmatis. Mycobactin formation in another strain of M. smegmatis, NCIB 8548, showed similar dependencies on Fe(2+), Zn(2+), and Mn(2+). Maximum accumulation of mycobactin with this strain was 85 mug of mycobactin/mg of dry cell weight, under iron-deficient (1.8 mum Fe(2+)) conditions.

Bacteriological Techniques↗