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PubMed2004

Ability of thermophilic lactic acid bacteria to produce aroma compounds from amino acids.

Although a large number of key odorants of Swiss-type cheese result from amino acid catabolism, the amino acid catabolic pathways in the bacteria present in these cheeses are not well known. In this study, we compared the in vitro abilities of Lactobacillus delbrueckii subsp. lactis, Lactobacillus helveticus, and Streptococcus thermophilus to produce aroma compounds from three amino acids, leucine, phenylalanine, and methionine, under mid-pH conditions of cheese ripening (pH 5.5), and we investigated the catabolic pathways used by these bacteria. In the three lactic acid bacterial species, amino acid catabolism was initiated by a transamination step, which requires the presence of an alpha-keto acid such as alpha-ketoglutarate (alpha-KG) as the amino group acceptor, and produced alpha-keto acids. Only S. thermophilus exhibited glutamate dehydrogenase activity, which produces alpha-KG from glutamate, and consequently only S. thermophilus was capable of catabolizing amino acids in the reaction medium without alpha-KG addition. In the presence of alpha-KG, lactobacilli produced much more varied aroma compounds such as acids, aldehydes, and alcohols than S. thermophilus, which mainly produced alpha-keto acids and a small amount of hydroxy acids and acids. L. helveticus mainly produced acids from phenylalanine and leucine, while L. delbrueckii subsp. lactis produced larger amounts of alcohols and/or aldehydes. Formation of aldehydes, alcohols, and acids from alpha-keto acids by L. delbrueckii subsp. lactis mainly results from the action of an alpha-keto acid decarboxylase, which produces aldehydes that are then oxidized or reduced to acids or alcohols. In contrast, the enzyme involved in the alpha-keto acid conversion to acids in L. helveticus and S. thermophilus is an alpha-keto acid dehydrogenase that produces acyl coenzymes A.

Amino Acids↗

PubMed1980

Oxidoreductase activities in normal rat liver, tumor-bearing rat liver, and hepatoma HC-252.

Experiments were carried out to determine if the difference in rates of cell proliferation between normal and neoplastic cells may be related to altered levels of oxidative enzymes. Assays were performed using homogenates from hepatocellular carcinoma HC-252, a rapidly growing and moderately well-differentiated tumor; from normal liver; and from the liver of the tumor-bearing ACI rat. Results of the mitochondrial enzymes indicated that the activities of cytochrome oxidase and succinate dehydrogenase were 3-fold lower in tumor homogenates than in liver homogenates. Monoamine oxidase activity could not be detected in HC-252; mixing experiments indicated no inhibitor was present in HC-252. Activities of th peroxisomal enzymes, urate oxidase, D-amino acid oxidase, and L-alpha-hydroxy acid oxidase were either undetected in the tumor or were 12-fold lower than in liver homogenates. The activity of xanthine oxidase, a cytoplasmic enzyme, was 5- to 6-fold lower in the tumor. Catalase activity in the tumor was also lower than in liver; this may be indicative of a lower oxidative environment at the cellular level. These enzyme activities of the liver of tumor-bearing rats were in the same range as those of normal rat liver, except that D-amino acid oxidase activity was slightly lower, and catalase activity was markedly lower and varied in a wide range. These results show an inverse correlation between the activities of oxygen-utilizing enzymes and rates of proliferation of one tumor line and its control. The possible implications of these results in neoplasia, cell proliferation, and cellular aging are discussed.

Animals↗

PubMed1998

Treatment of warts with topical pyruvic acid: with and without added 5-fluorouracil.

Pyruvic acid (PA) is an alpha-hydroxy acid with potent keratolytic properties. Fifty-six patients with common warts treated with two PA formulations were surveyed 2 to 29 months after beginning treatment (mean, 18 months). Thirty-eight patients used a 70 percent PA formulation with added 0.5 percent 5-fluorouracil (PA-5FU). Eighteen patients used a plain 70 percent PA formulation without added 5FU. Three-quarters of the patients reported using the formulation for 4 weeks or less. Overall, 64 percent of the patients treated with either of the two formulations experienced complete clearing of their lesions. There was no increased efficacy noted with the PA-5FU formulation. Eighty-two percent of eighteen children, aged 16 years or younger, experienced clearing of lesions.

Administration, Topical↗

PubMed2002

The synthesis of short- and medium-chain-length poly(hydroxyalkanoate) mixtures from glucose- or alkanoic acid-grown Pseudomonas oleovorans.

Pseudomonas oleovorans NRRL B-778 accumulated mixtures of poly-3-hydroxybutyrate (PHB) and medium-chain-length poly(hydroxyalkanoates) (mcl-PHAs) when grown on glucose, octanoic acid or oleic acid, whereas growth on nonanoic acid or undecanoic acid resulted in copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV). Acetone fractionation verified the presence of PHB/mcl-PHA mixtures. The acetone-insoluble (AIS) fractions of the polymers derived from glucose (PHA-glucose), octanoic acid (PHA-octanoic) and oleic acid (PHA-oleic) were exclusively PHB while the acetone-soluble (AS) fractions contained mcl-PHA composed of differing ratios of 3-hydroxy-acid monomer units, which ranged in chain length from 6 to 14 carbon atoms. In contrast, both the AIS and AS fractions from the polymers derived from nonanoic acid (PHA-nonanoic) and undecanoic acid (PHA-undecanoic) were composed of comparable ratios of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). The unfractionated PHA-glucose, PHA-octanoic and PHA-oleic polymers had melting temperatures (Tm) between 177 and 179 degrees C, enthalpies of fusion (AHf) of 20 cal/g and glasstransition temperatures (Tg) of 3-4 degrees C. This was due to the large PHB content in the polymer mixtures. On the other hand, the PHA-nonanoic and PHA-undecanoic polymers had thermal properties that supported their copolymer nature. In both cases, the Tm values were 161 degrees C, deltaHf values were 7 cal/g and Tg values were - 3 degrees C.

Fermentation↗

PubMed2005

Stereoselective syntheses of 4-hydroxy 4-substituted glutamic acids.

The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition.

Alanine↗

PubMed1995

Thermodynamics of Strecker synthesis in hydrothermal systems.

Submarine hydrothermal systems on the early Earth may have been the sites from which life emerged. The potential for Strecker synthesis to produce biomolecules (amino and hydroxy acids) from starting compounds (ketones, aldehydes, HCN and ammonia) in such environments is evaluated quantitatively using thermodynamic data and parameters for the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Although there is an overwhelming thermodynamic drive to form biomolecules by the Strecker synthesis at hydrothermal conditions, the availability and concentration of starting compounds limit the efficiency and productivity of Strecker reactions. Mechanisms for concentrating reactant compounds could help overcome this problem, but other mechanisms for production of biomolecules may have been required to produce the required compounds on the early Earth. Geochemical constraints imposed by hydrothermal systems provide important clues for determining the potential of these and other systems as sites for the emergence of life.

Aldehydes↗

PubMed2005

An experimental and theoretical investigation of the photophysics of 1-hydroxy-2-naphthoic acid.

Photophysical and photochemical properties of 1-hydroxy-2-naphthoic acid (1,2-HNA) have been investigated experimentally by steady state and time domain fluorescence measurements and theoretically by Hartree-Fock (HF), configuration interaction at the single excitation (CIS) level, density functional theoretic (DFT), and semiempirical (AM1) methods. 1,2-HNA exhibits normal fluorescence that depends on its concentration, nature of the solvent, pH, temperature, and wavelength of excitation. It seems to form different emitting species in different media, akin to 3-hydroxy-2-naphthoic acid (3,2-HNA). The large Stokes shifted emission observed at pH 13 is attributed to species undergoing excited-state intramolecular proton transfer. Nonradiative transition seems to increase on protonation and decrease on deprotonation. AM1(PECI=8) calculations predict the absorption maximum (lambda(max) = 335.9 nm) in reasonable agreement with experiment (lambda(max) = 352 nm) for the neutral 1,2-HNA. They also predict a red shift in absorption on protonation and a blue shift on deprotonation as observed experimentally. CIS calculations tend to overestimate the energy gap and hence underestimate the absorption maxima between the ground and the excited electronic states of 1,2-HNA and its protonated and deprotonated forms. However, they do predict correctly that the excited state intramolecular proton transfer is likely to occur in the deprotonated form of 1,2-HNA and not in the neutral and the protonated forms. A single minimum is found in the potential energy profile for the ground state as well as the first excited state of 1,2-HNA and its protonated species. In contrast, a double minimum with a nominal barrier in between is predicted for the ground state and also the first three excited states of the deprotonated species. The keto form of the deprotonated species is found to be slightly less stable than the enol form in all the states investigated.

Journal Article↗

PubMed2003

The inhibitory effect of glycolic acid and lactic acid on melanin synthesis in melanoma cells.

Alpha-hydroxy acids (AHAs) such as glycolic acid (GA) and lactic acid (LA) have been reported to be effective in treating pigmentary lesions such as melasma, solar lentigines, and postinflammatory hyperpigmentation. The mechanism of this effect might be due to epidermal remodeling and accelerated desquamation, which would result in quick pigment dispersion. However, the direct effect of AHAs on melanin synthesis has not yet been well studied. To elucidate such a direct effect of AHAs on melanogenesis, we performed melanin assays, growth curve determinations, Northern and Western blotting for melanogenic proteins [tyrosinase, tyrosinase related protein (TRP)-1 and TRP-2], and tyrosinase and, 4-dihydroxyphenylalaninechrome tautomerase enzyme activity assays using mouse B16 and human melanoma cells. GA or LA (at doses of 300 or 500 microg/ml) inhibited melanin formation in similar dose-dependent manner, without affecting cell growth. Although the mRNA and protein expression or molecular size of tyrosinase, TRP-1 and TRP-2 were not affected, tyrosinase activity was inhibited. To see whether GA and/or LA directly inhibit tyrosinase catalytic function, the effect of GA and LA on human tyrosinase purified from the melanosome-rich large granule fraction of human melanoma cells was performed. GA or LA were shown to inhibit tyrosinase enzyme activity directly, but this effect was not due to the acidity of GA or LA, because adjusting the pH to 5.6 (the pH of GA and LA at concentrations of 2500 microg/ml), did not affect tyrosinase activity. Taken together, these results show that GA and LA suppress melanin formation by directly inhibiting tyrosinase activity, an effect independent of their acidic nature. GA and LA might work on pigmentary lesions not only by accelerating the turnover of the epidermis but also by directly inhibiting melanin formation in melanocytes.

Animals↗

PubMed1983

Aerobic and Anaerobic Catabolism of Vanillic Acid and Some Other Methoxy-Aromatic Compounds by Pseudomonas sp. Strain PN-1.

Vanillic acid (4-hydroxy-3-methoxybenzoic acid) supported the anaerobic (nitrate respiration) but not the aerobic growth of Pseudomonas sp. strain PN-1. Cells grown anaerobically on vanillate oxidized vanillate, p-hydroxybenzoate, and protocatechuic acid (3,4-dihydroxybenzoic acid) with O(2) or nitrate. Veratric acid (3,4-dimethoxybenzoic acid) but not isovanillic acid (3-hydroxy-4-methoxybenzoic acid) induced cells for the oxic and anoxic utilization of vanillate, and protocatechuate was detected as an intermediate of vanillate breakdown under either condition. Aerobic catabolism of protocatechuate proceeded via 4,5-meta cleavage, whereas anaerobically it was probably dehydroxylated to benzoic acid. Formaldehyde was identified as a product of aerobic demethylation, indicating a monooxygenase mechanism, but was not detected during anaerobic demethylation. The aerobic and anaerobic systems had similar but not identical substrate specificities. Both utilized m-anisic acid (3-methoxybenzoic acid) and veratrate but not o- or p-anisate and isovanillate. Syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 3-O-methylgallic acid (3-methoxy-4,5-dihydroxybenzoic acid), and 3,5-dimethoxybenzoic acid were attacked under either condition, and formaldehyde was liberated from these substrates in the presence of O(2). The anaerobic demethylating system but not the aerobic enzyme was also active upon guaiacol (2-methoxyphenol), ferulic acid (3-[4-hydroxy-3-methoxyphenyl]-2-propenoic acid), 3,4,5-trimethoxycinnamic acid (3-[3,4,5-trimethoxyphenyl]-2-propenoic acid), and 3,4,5-trimethoxybenzoic acid. The broad specificity of the anaerobic demethylation system suggests that it probably is significant in the degradation of lignoaromatic molecules in anaerobic environments.

Journal Article↗

PubMed1998

Saralasin-induced inhibition of ovulation in the in vitro perfused rat ovary is not replicated by the angiotensin II type-2 receptor antagonist PD123319.

OBJECTIVE: Our aim was to explain the effect of the nonspecific angiotensin II antagonist saralasin and the specific angiotensin II type-2 receptor antagonist PD123319 on ovulation. STUDY DESIGN: Saralasin, 1 micromol/L (n = 5), and PD123319 10 micromol/L (n = 6), were administered to in vitro perfused rat ovary. Prostaglandin (prostaglandin E2, prostaglandin F2alpha, 6-keto-prostaglandin F1alpha), hydroxy-eicosatetraenoic acid (12-hydroxy-eicosatetraenoic acid, 15-hydroxy-eicosatetraenoic acid), estradiol, and progesterone levels in the perfusate and the ovulation rate were compared (Mann-Whitney U test) with controls. RESULTS: Saralasin significantly (P < .01) inhibited the ovulation rate (3.0 +/- 1.4) versus control (13.1 +/- 1.0) and reduced prostaglandin E2 (at 3 hours P < .01 and 20 hours P < .05) and 6-keto-prostaglandin F1alpha (at 20 hours P < .05) levels. Saralasin did not alter prostaglandin F2alpha, hydroxy-eicosatetraenoic acids, or steroid levels. PD123319 decreased 15-hydroxy-eicosatetraenoic acid levels at 3 hours (P < .05) but had no effects on other eicosanoids, steroid levels, or the ovulation rate. CONCLUSION: Angiotensin II plays an important role in ovulation in the rat and is associated with ovarian prostaglandin synthesis. This effect is not selectively regulated via the angiotensin II type-2 receptor.

Angiotensin Receptor Antagonists↗

PubMed1997

An experimental approach to evaluating the role of backbone interactions in proteins using unnatural amino acid mutagenesis.

The contribution of backbone hydrogen bonds in alpha-helices to the overall stability of a protein has been examined experimentally by replacing several backbone amide linkages in alpha-helix 39-50 of T4 lysozyme with ester linkages. T4 lysozyme variants wherein the backbone amide bonds between residues Ser38 and Leu39, Lys43 and Leu44, or Ala49 and Ile50 are replaced with ester bonds were generated by incorporating alpha-hydroxy acids at positions 39, 44, or 50, respectively, using unnatural amino acid mutagenesis. The stabilities of the proteins were determined from their thermal denaturation curves as monitored by circular dichroism. Comparison of the thermal stabilities of the amide- and ester-containing proteins shows that the ester substitution has a similar thermodynamic effect at all three positions. At the N- and C-terminal positions, where only one hydrogen-bonding interaction is perturbed, the ester substitution is destabilizing by 0.9 and 0.7 kcal/mol, respectively. Introduction of the ester linkage in the middle of the helix, which alters two hydrogen-bonding interactions, destabilizes the protein by 1.7 kcal/mol. The values obtained from these ester to amide mutations are compared to the values from similar mutations that have been made in other secondary structures and bimolecular complexes.

Acylation↗

PubMed1989

Peroxisomal oxidases: cytochemical localization and biological relevance.

(1) alpha-HAOX has a broad substrate specificity. In rat kidney, the enzyme reacts with aliphatic and aromatic alpha-hydroxy acids, in rat liver, however, only with aliphatic ones. (2) The best substrate for the demonstration of alpha-HAOX activity in rat and human liver is glycolate. (3) alpha-hydroxy butyric acid is the best substrate in the luminometric assay for the demonstration of alpha-HAOX activity in the rat kidney, whereas glycolate is not catalysed by the enzyme. (4) In the proximal tubulus epithelial cells of the rat kidney alpha-HAOX is concentrated in the peripheral matrix of the peroxisomes.

Alcohol Oxidoreductases↗

PubMed1978

4-hydroxy-3-methoxymandelic acid (HMMA) excretion in retinoblastoma.

4-Hydroxy-3-methoxymandelic acid (HMMA) concentrations in aqueous humour, urine, and serum were simultaneously estimated to determine if these levels were raised in cases of retinoblastoma. The catecholamine content of aqueous humour was significantly higher than that of urine and serum, but as there was no significant difference in the HMMA concentration in retinoblastoma and other non-malignant conditions it seems likely that retinoblastoma is not a catecholamine-secreting tumour.

Aged↗

PubMed1975

Atomic absorption spectrophotometric determination of 4-hydroxy-3-nitrobenzenearsonic acid (roxarsone) in premixes.

Roxarsone (4-hydroxy-3-nitrobenzenearsonic acid) is extracted from the premix with aqueous 1% ammonium carbonate. The extract is filtered, diluted, and analyzed by atomic absorption spectrophotometry, using an air-acetylene flame and an arsenic electrodeless discharge lamp. The instrument response of the sample is compared to that of a standard solution of arsenic trioxide. Recoveries range from 99.7. to 100.4% and coefficients of variation range from 0.35 to 0.63%.

Animal Feed↗

PubMed1989

Fluorescence polarization immunoassay of urinary 5-hydroxy-3-indoleacetic acid.

Fluorescence polarization immunoassay of 5-hydroxy-3-indoleacetic acid in urine is described and compared with liquid chromatography (electrochemical detection) and colorimetry. Reports of in-house performance data and results of clinical trials are included to emphasize the usefulness of the assay for routine work.

Chromatography, High Pressure Liquid↗

PubMed2005

Lactate racemization as a rescue pathway for supplying D-lactate to the cell wall biosynthesis machinery in Lactobacillus plantarum.

Lactobacillus plantarum is a lactic acid bacterium that produces d- and l-lactate using stereospecific NAD-dependent lactate dehydrogenases (LdhD and LdhL, respectively). However, reduction of glycolytic pyruvate by LdhD is not the only pathway for d-lactate production since a mutant defective in this activity still produces both lactate isomers (T. Ferain, J. N. Hobbs, Jr., J. Richardson, N. Bernard, D. Garmyn, P. Hols, N. E. Allen, and J. Delcour, J. Bacteriol. 178:5431-5437, 1996). Production of d-lactate in this species has been shown to be connected to cell wall biosynthesis through its incorporation as the last residue of the muramoyl-pentadepsipeptide peptidoglycan precursor. This particular feature leads to natural resistance to high concentrations of vancomycin. In the present study, we show that L. plantarum possesses two pathways for d-lactate production: the LdhD enzyme and a lactate racemase, whose expression requires l-lactate. We report the cloning of a six-gene operon, which is involved in lactate racemization activity and is positively regulated by l-lactate. Deletion of this operon in an L. plantarum strain that is devoid of LdhD activity leads to the exclusive production of l-lactate. As a consequence, peptidoglycan biosynthesis is affected, and growth of this mutant is d-lactate dependent. We also show that the growth defect can be partially restored by expression of the d-alanyl-d-alanine-forming Ddl ligase from Lactococcus lactis, or by supplementation with various d-2-hydroxy acids but not d-2-amino acids, leading to variable vancomycin resistance levels. This suggests that L. plantarum is unable to efficiently synthesize peptidoglycan precursors ending in d-alanine and that the cell wall biosynthesis machinery in this species is specifically dedicated to the production of peptidoglycan precursors ending in d-lactate. In this context, the lactate racemase could thus provide the bacterium with a rescue pathway for d-lactate production upon inactivation or inhibition of the LdhD enzyme.

Amino Acids↗

PubMed1979

Conversion by rat brain preparation of lignoceric acid to ceramides and cerebrosides containing both alpha-hydroxy and nonhydroxy fatty acids. Effects of compounds which affect sphingolipid metabolism.

Three synthetic compounds which affect sphingolipid metabolism in vitro were examined for their effects on the synthesis in a rat brain system of nonhydroxyceramide, hydroxyceramide, nonhydroxycerebroside, and hydroxycerebroside from [1-14C]ignoceric acid. These compounds are N-octanoyl-D-threo-p-nitrophenylaminopropanediol (Compound I), N-(2,3-epoxydecanoyl)-norephedrine (Compound II), and N-decyl-N'-glucosylthiourea (Compound III). In the presence of up to 0.5 mM Compound I, only the hydroxyceramide fromation increased, while the synthesis of the other three lipids decreased. Compound II strongly inhibited the formation of all four lipids at all concentrations tested (0.1 to 1 mM). Compound III increased the synthesis of both ceramides approximately 2-fold at 1 mM, but the conversion of lignoceric acid to both cerebrosides remained relatively unchanged. Several significant conclusions from these observations are discussed.

Animals↗

PubMed1990

The linoleic acid metabolite 9DS-hydroxy-10,12(E,Z)-octadecadienoic acid is a strong proinflammatory mediator in an experimental wound healing model of the rat.

Locally administered 9Ds-hydroxy-10,12(E,Z)-octadecadienoic acid (9-HODE) caused a drastic inflammatory response in the experimental model of granulation tissue formation of the rat according to RUDAS (Arzneimittelforsch. 10,226-229, 1960). Three days after implantation of the polyvinyl chloride rings the granulation tissue became inhomogeneous with proliferation islets surrounded by edematous regions containing a diminished number of cells. The number of polymorphonuclear leukocytes and of macrophages was greatly enhanced in the whole tissue, whereas the number of lymphocytes was reduced. After seven days the whole granulation tissue was loosened, and its mass was twice as high as in the control animals. The number of fibroblasts per area unit and the hydroxyproline content were diminished. Linoleic acid and 13Ls-hydroxy-9,11(Z,E)-octadecadienoic acid (13-HODE) caused also some changes in the formation of granulation tissue, but in a different manner, in particular, without accumulation of polymorphonuclear leukocytes and macrophages, indicating the specificity of the effect of 9-HODE. The recruitment of leukocytes was not due to a direct chemotactic action of 9-HODE as shown in an agarose diffusion test comparing the effects of 9-HODE and leukotriene B4. The possible biological importance of the proinflammatory effect of 9-HODE is discussed.

Animals↗