salicylates and salicyl-alcohol

The volatile compounds that constitute the fruit aroma of ripe tomato (Solanum lycopersicum) are often sequestered in glycosylated form. A homology-based screen was used to identify the gene SlUGT5, which is a member of UDP-glycosyltransferase 72 family and shows specificity towards a range of substrates, including flavonoid, flavanols, hydroquinone, xenobiotics and chlorinated pollutants. SlUGT5 was shown to be expressed primarily in ripening fruit and flowers, and mapped to chromosome I in a region containing a QTL that affected the content of guaiacol and eugenol in tomato crosses. Recombinant SlUGT5 protein demonstrated significant activity towards guaiacol and eugenol, as well as benzyl alcohol and methyl salicylate; however, the highest in vitro activity and affinity was shown for hydroquinone and salicyl alcohol. NMR analysis identified isosalicin as the only product of salicyl alcohol glycosylation. Protein modelling and substrate docking analysis were used to assess the basis for the substrate specificity of SlUGT5. The analysis correctly predicted the interactions with SlUGT5 substrates, and also indicated that increased hydrogen bonding, due to the presence of a second hydrophilic group in methyl salicylate, guaiacol and hydroquinone, appeared to more favourably anchor these acceptors within the glycosylation site, leading to increased stability, higher activities and higher substrate affinities.

Topics: Amino Acid Sequence; Benzyl Alcohol; Benzyl Alcohols; Catalytic Domain; Chromosomes; Cloning, Molecular; Escherichia coli; Eugenol; Gene Expression; Glycosyltransferases; Guaiacol; Hydrogen Bonding; Hydroquinones; Models, Molecular; Molecular Sequence Data; Phenols; Phenylethyl Alcohol; Phylogeny; Plant Proteins; Plant Structures; Recombinant Proteins; Salicylates; Sequence Homology, Amino Acid; Solanum lycopersicum; Substrate Specificity; Uridine Diphosphate Glucose; Volatile Organic Compounds

Since the growth of wild-type Escherichia coli in salicylate results in a multiple antibiotic resistance phenotype similar to that of constitutive mutants (Mar) of the chromosomal mar locus, the effect of salicylate on the expression of the marRAB operon was investigated. The amount of RNA hybridizing with a mar-specific DNA probe was 5 to 10 times higher in wild-type cells grown with sodium salicylate (5.0 mM) than in untreated controls. Untreated Mar mutants had three to five times more mar-specific RNA than wild-type cells did. When a Mar mutant was treated with salicylate, a 30- to 50-fold increase of mar-specific RNA was seen. In wild-type cells bearing a mar promoter-lacZ fusion on the chromosome, salicylate increased beta-galactosidase activity by sixfold. Thus, salicylate induces transcription of the marRAB operon. Other inducers of phenotypic multiple antibiotic resistance, e.g., benzoate, salicyl alcohol, and acetaminophen, but not acetate, also increased transcription from the mar promoter but to a lesser extent than did salicylate. Both in wild-type and mar-deficient strains, growth in salicylate resulted in increased antibiotic resistance, decreased permeation of the outer membrane to cephaloridine, increased micF transcription, and decreased amounts of OmpF. However, the magnitude of these changes was generally greater in wild-type (mar-containing) cells. Thus, salicylate and other compounds can induce transcription of the mar operon and, presumably, give rise to multiple antibiotic resistance via this pathway. However, salicylate can also activate an unidentified, mar-independent pathway(s) which engenders multiple antibiotic resistance.

Topics: Ampicillin; Anti-Bacterial Agents; Bacterial Outer Membrane Proteins; Benzyl Alcohols; beta-Galactosidase; Chloramphenicol; Chromosomes, Bacterial; Drug Resistance, Microbial; Escherichia coli; Gene Expression Regulation, Bacterial; Genotype; Microbial Sensitivity Tests; Operon; Recombinant Fusion Proteins; RNA, Bacterial; Salicylates; Salicylic Acid; Tetracycline; Transcription, Genetic

The toxicity of Cd2+ in Escherichia coli K-12 was potentiated by salicylate and several related compounds. The efficiency of plating on Luria broth plates was reduced by more than 10(5)-fold when 10 mM salicylate and 200 microM CdCl2 were present simultaneously but was unaffected when either compound was present by itself. Synergistic effects were found at pH 7.4 with certain other weak acids (acetyl salicylate [aspirin], benzoate, and cinnamate) and with a nonacidic salicylate analog, salicyl alcohol, but not with acetate or p-hydroxy benzoate. Thus, the synergism with Cd2+ is determined by the structure of the compounds and not merely by their acidity. The kinetics of 109Cd2+ uptake by cells grown and assayed in broth indicated the presence of two uptake systems with Kms of 1 and 52 microM Cd2+ and Vmaxs of 0.059 and 1.5 mumol of Cd2+ per min per g of cells, respectively. The kinetics of uptake for cells grown and assayed with 20 mM salicyl alcohol showed 2.5-fold increases in the Vmaxs of both systems but no change in the Kms. Salicylate-grown cells also exhibited increased rates of 109Cd2+ uptake by both systems. Thus, enhanced uptake of Cd2+ may be responsible for the potentiation of Cd2+ toxicity by salicylate and salicyl alcohol.

Topics: Acetates; Benzyl Alcohols; Cadmium; Cadmium Radioisotopes; Culture Media; Drug Synergism; Escherichia coli; Hydrogen-Ion Concentration; Kinetics; Membrane Potentials; Salicylates; Salicylic Acid

Susceptibility of Escherichia coli to kanamycin and seven other aminoglycosides has been found to be strongly potentiated by salicylate. At pH 7.5, in the presence of 15 mM salicylate and 0.5 micrograms of kanamycin per ml, the efficiency of plating of the bacteria was 2 x 10(-5), whereas there was no significant killing in the presence of kanamycin or salicylate alone. With 0.75 micrograms of kanamycin per ml, the addition of 2.5 mM salicylate was sufficient to reduce the efficiency of plating by more than 10(4)-fold. Synergistic effects were found also at pHs 6.5 and 8.5. To determine whether the action of salicylate resulted from its behavior as a weak acid or its salicyl structure, similar experiments were carried out with acetate and salicyl alcohol. Acetate, a membrane-permeating weak acid, showed a synergistic effect on kanamycin susceptibility at pH 6.5 that was comparable to the effect seen with salicylate at pH 6.5. However, acetate had no synergistic effect with kanamycin at pH 7.5 or 8.5. This is consistent with the ability of acetate to increase the membrane potential of cells and the dependence of susceptibility to kanamycin and other aminoglycosides on the membrane potential. Salicyl alcohol, which has a hydroxyl group in the place of the carboxyl group that is present in salicylate, was an effective synergist with kanamycin. It was equally effective at pHs 6.5 and 7.5 and somewhat more effective at pH 8.5. These results support the hypothesis that two effects are involved in the synergy between aminoglycosides and salicylate: a weak acid effect, possibly to increase the membrane potential, and an uncharacterized effect related to the salicyl structure.

Topics: Acetates; Anti-Bacterial Agents; Benzyl Alcohols; Drug Synergism; Escherichia coli; Hydrogen-Ion Concentration; Kanamycin; Microbial Sensitivity Tests; Salicylates

Topics: Alcohols; Benzyl Alcohols; Neurospora; Salicylates