A kinetic study on benzoic acid pungency and sensory attributes of benzoic acid.
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Aqueous solutions of benzoic acid (BA) were evaluated by two methods: (i) sensory profile: a descriptive test of sensory attributes combined with semiquantitative analysis; and (ii) pungency intensity measures as a function of time: a computerized recording using specific software. Kinetic parameters evaluated were maximal intensity (I(MAX)), total time of pungency (Ttot), rates of increase (V1) and decrease (V2), half-life (T1/2), area under curve (AUC) and time to maximal intensity (T(IMAX)). Results were analyzed by ANOVA, LSD test, iterative calculations and adjustment to equations according to mathematical models, regression analysis, principal component analysis (PCA) and clusters analysis. Pungency was the main sensory attribute of BA (3-36 mM) in the tongue and epiglottis. The seven kinetic parameters showed concentration-dependency (P < 0.001) and were described by different functions: (i) lineal: I(MAX) = 2.24 +/- 0.14C - 3.06 +/- 2.58, R2 = 0.98; T(IMAX) = 0.19 +/- 0.02C + 6.87 +/- 0.47, R2 = 0.92; V1 = 0.68 +/- 0.03C + 0.10 +/- 0.69, R2 = 0.99; AUC = 49.10 +/- 3.17C - 230.78 +/- 59.66, R2 = 0.98; (ii) potency: T1/2 = 6.62 +/- 0.61C(0.39+/-0.03), R2 = 0.97; V2 = 1.07 +/- 0.11C(0.53+/-0.04), R2 = 0.98; Ttot = 8.08 +/- 1.01C(0.43+/-0.04), R2 = 0.96. PCA revealed high correlation between (i) T(IMAX) and Ttot; (ii) T1/2 and V2; and (iii) I(MAX) and V1. Stimuli grouped across three main clusters: (i) 3 and 6 mM; (ii) 9, 12 and 18 mM; and (iii) 24 and 36 mM. Maximal pungency intensity best correlated with both concentration and persistence among kinetic parameters. Prototypical prickling of BA was observed at 12 and 18 mM. (+info)
Chemicals in laboratory room air stimulate olfactory neurons of female Bombyx mori.
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Laboratory air contained odorants that elicited electrophysiological responses in female Bombyx mori antennae. Air entrainments on charcoal filters, extracted with CS(2) and subsequently with acetone, were analyzed by coupled gas chromatography (GC)-electroantennogram (EAG) as well as by GC-mass spectrometry. The CS(2) extract contained 12 EAG-active peaks from which benzaldehyde, octanal, limonene, 1,8-cineol, methyl benzoate, nonanal, decanal and geranyl acetone were identified. In the acetone extract we identified eight EAG-active peaks as phenol, nonanal, 2-ethylhexanoic acid, octanoic acid, benzoic acid, nonanoic acid, decanoic acid and dimethyl phthalate. The concentrations of benzoic acid and benzaldehyde present in laboratory air were determined. The origin of the substances and importance of such odorants in laboratory air for the interpretation of physiological experiments on the olfactory system is discussed. (+info)
Gene cloning and nucleotide sequencing and properties of a cocaine esterase from Rhodococcus sp. strain MB1.
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A strain of Rhodococcus designated MB1, which was capable of utilizing cocaine as a sole source of carbon and nitrogen for growth, was isolated from rhizosphere soil of the tropane alkaloid-producing plant Erythroxylum coca. A cocaine esterase was found to initiate degradation of cocaine, which was hydrolyzed to ecgonine methyl ester and benzoate; both of these esterolytic products were further metabolized by Rhodococcus sp. strain MB1. The structural gene encoding a cocaine esterase, designated cocE, was cloned from Rhodococcus sp. strain MB1 genomic libraries by screening recombinant strains of Rhodococcus erythropolis CW25 for growth on cocaine. The nucleotide sequence of cocE corresponded to an open reading frame of 1,724 bp that codes for a protein of 574 amino acids. The amino acid sequence of cocaine esterase has a region of similarity with the active serine consensus of X-prolyl dipeptidyl aminopeptidases, suggesting that the cocaine esterase is a serine esterase. The cocE coding sequence was subcloned into the pCFX1 expression plasmid and expressed in Escherichia coli. The recombinant cocaine esterase was purified to apparent homogeneity and was found to be monomeric, with an M(r) of approximately 65,000. The apparent K(m) of the enzyme (mean +/- standard deviation) for cocaine was measured as 1.33 +/- 0.085 mM. These findings are of potential use in the development of a linked assay for the detection of illicit cocaine. (+info)
A 90-kilobase conjugative chromosomal element coding for biphenyl and salicylate catabolism in Pseudomonas putida KF715.
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The biphenyl and salicylate metabolic pathways in Pseudomonas putida KF715 are chromosomally encoded. The bph gene cluster coding for the conversion of biphenyl to benzoic acid and the sal gene cluster coding for the salicylate meta-pathway were obtained from the KF715 genomic cosmid libraries. These two gene clusters were separated by 10-kb DNA and were highly prone to deletion when KF715 was grown in nutrient medium. Two types of deletions took place at the region including only the bph genes (ca. 40 kb) or at the region including both the bph and sal genes (ca. 70 kb). A 90-kb DNA region, including both the bph and sal genes (termed the bph-sal element), was transferred by conjugation from KF715 to P. putida AC30. Such transconjugants gained the ability to grow on biphenyl and salicylate as the sole sources of carbon. The bph and sal element was located on the chromosome of the recipient. The bph-sal element in strain AC30 was also highly prone to deletion; however, it could be mobilized to the chromosome of P. putida KT2440 and the two deletion mutants of KF715. (+info)
Novel scheme for biosynthesis of aryl metabolites from L-phenylalanine in the fungus Bjerkandera adusta.
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Aryl metabolite biosynthesis was studied in the white rot fungus Bjerkandera adusta cultivated in a liquid medium supplemented with L-phenylalanine. Aromatic compounds were analyzed by gas chromatography-mass spectrometry following addition of labelled precursors ((14)C- and (13)C-labelled L-phenylalanine), which did not interfere with fungal metabolism. The major aromatic compounds identified were benzyl alcohol, benzaldehyde (bitter almond aroma), and benzoic acid. Hydroxy- and methoxybenzylic compounds (alcohols, aldehydes, and acids) were also found in fungal cultures. Intracellular enzymatic activities (phenylalanine ammonia lyase, aryl-alcohol oxidase, aryl-alcohol dehydrogenase, aryl-aldehyde dehydrogenase, lignin peroxidase) and extracellular enzymatic activities (aryl-alcohol oxidase, lignin peroxidase), as well as aromatic compounds, were detected in B. adusta cultures. Metabolite formation required de novo protein biosynthesis. Our results show that L-phenylalanine was deaminated to trans-cinnamic acid by a phenylalanine ammonia lyase and trans-cinnamic acid was in turn converted to aromatic acids (phenylpyruvic, phenylacetic, mandelic, and benzoylformic acids); benzaldehyde was a metabolic intermediate. These acids were transformed into benzaldehyde, benzyl alcohol, and benzoic acid. Our findings support the hypothesis that all of these compounds are intermediates in the biosynthetic pathway from L-phenylalanine to aryl metabolites. Additionally, trans-cinnamic acid can also be transformed via beta-oxidation to benzoic acid. This was confirmed by the presence of acetophenone as a beta-oxidation degradation intermediate. To our knowledge, this is the first time that a beta-oxidation sequence leading to benzoic acid synthesis has been found in a white rot fungus. A novel metabolic scheme for biosynthesis of aryl metabolites from L-phenylalanine is proposed. (+info)
Developmental regulation of methyl benzoate biosynthesis and emission in snapdragon flowers.
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In snapdragon flowers, the volatile ester methyl benzoate is the most abundant scent compound. It is synthesized by and emitted from only the upper and lower lobes of petals, where pollinators (bumblebees) come in contact with the flower. Emission of methyl benzoate occurs in a rhythmic manner, with maximum emission during the day, which correlates with pollinator activity. A novel S-adenosyl-l-methionine:benzoic acid carboxyl methyl transferase (BAMT), the final enzyme in the biosynthesis of methyl benzoate, and its corresponding cDNA have been isolated and characterized. The complete amino acid sequence of the BAMT protein has only low levels of sequence similarity to other previously characterized proteins, including plant O-methyl transferases. During the life span of the flower, the levels of methyl benzoate emission, BAMT activity, BAMT gene expression, and the amounts of BAMT protein and benzoic acid are developmentally and differentially regulated. Linear regression analysis revealed that production of methyl benzoate is regulated by the amount of benzoic acid and the amount of BAMT protein, which in turn is regulated at the transcriptional level. (+info)
Allosteric inhibition of endothelin ETA receptors by 3, 5-dibromosalicylic acid.
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Derivatives of salicylic acid (SA) and benzoic acid prevent endothelin-1 (ET-1) binding to ETA receptors. This study analyzed actions of 30 derivatives of benzoic acid and salicylic acid on (125)I-ET-1 binding to recombinant rat ETA receptors. The most active compounds were 3,5-dibromosalicylic acid (Br2SA, K(i) = 0.5 mM) and 3,5-diiodosalicylic acid (K(i) = 0.3 mM). They were about 50 times more potent than SA and aspirin. Br2SA inhibited equilibrium (125)I-ET-1 binding in an apparently competitive manner. It accelerated 8-fold the dissociation of (125)I-ET-1 receptor complexes and did not modify the second order rate constant of association of (125)I-ET-1 to its receptors. Br2SA also decreased the affinity of ETA receptors for receptor antagonists BQ-123 and bosentan. Br2SA accelerated dissociation of (125)I-ET-1-solubilized ETA receptor complexes and decreased the apparent molecular size of solubilized receptors. Br2SA and 3,5-diiodosalicylic acid inhibited two cellular actions of ET-1: the mobilization of intracellular Ca(2+) stores in isolated cells and contractions of rat aortic rings. They accelerated the relaxing action of BQ-123 and bosentan in ET-1-treated aortic rings. The results suggest the existence of an allosteric modifier site on ETA receptors that recognizes selected derivatives of SA. SA derivatives might be of therapeutic interest to relieve tight ET-1 binding and to favor actions of receptor antagonists. (+info)
Genetic manipulation of 6-phosphofructo-1-kinase and fructose 2,6-bisphosphate levels affects the extent to which benzoic acid inhibits the growth of Saccharomyces cerevisiae.
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The mechanisms by which the weak acid preservative benzoic acid inhibits the growth of Saccharomyces cerevisiae have been investigated. A reduction in the pyruvate kinase level, which decreases glycolytic flux, did not increase the sensitivity of yeast to benzoic acid. However, a decrease in 6-phosphofructo-1-kinase (PF1K), which does not affect glycolytic flux, did increase sensitivity to benzoic acid. Also, resistance was increased by elevating PF1K levels. Hence, resistance to benzoic acid was not dependent upon optimum glycolytic flux, but upon an adequate PF1K activity. Benzoic acid was shown to depress fructose 2,6-bisphosphate levels in YKC14, a mutant with low PF1K levels. This effect was partially suppressed by overexpressing constitutively active 6-phosphofructo-2-kinase (Pfk26(Asp644)) or by inactivating fructose-2,6-bisphosphatase (in a Deltafbp26 mutant). The inactivation of PF2K (in a Deltapfk26 Deltapfk27 mutant) increased benzoic acid sensitivity. Therefore, the antimicrobial effects of benzoic acid can be relieved, at least in part, by the genetic manipulation of PF1K or fructose 2,6-bisphosphate levels. (+info)