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PubMed1985

The aromatization of cyclohexanecarboxyl-CoA to hippuric acid by guinea pig liver mitochondria: submitochondrial localization.

The conversion of cyclohexanecarboxyl-CoA to hippuric acid in submitochondrial fractions from guinea pig liver was studied using a gas chromatographic-mass spectrometric method employing selected ion monitoring. Comparison of the activities of the cyclohexanecarboxyl-CoA to hippuric acid converting system (CCoAHC-system) and marker enzymes in the various submitochondrial fractions showed that the CCoAHC-system is localized in the mitochondrial matrix. Partial separation of the inner and outer membranes has been accomplished by treating mitochondria with digitonin in isotonic medium and fractionating the treated mitochondria by differential centrifugation. A digitonin-protein ratio of 2.6 mg of digitonin/10 mg of protein must be used in order to release significant amounts of amine oxidase activity (outer membrane marker) from low speed mitochondrial pellets. This pellet still contained most of the glutamate dehydrogenase activity and was insignificantly contaminated with adenylate kinase. Moderate concentrations of phenazine methosulfate (PMS) greatly stimulated the activity of the CCoAHC-system, even in intact mitochondria (optimal concentration of PMS: 1 mM) whilst higher concentrations (greater than 1 mM) decreased the activity. The formation of hippuric acid in these mitochondrial preparations was linear with time for at least 40 min and linear with respect to protein concentration up to approximately 2.0 mg mitochondrial protein X ml-1.

Acyl Coenzyme A↗
PubMed1982

The origin of urinary aromatic compounds excreted by ruminants. 1. The metabolism of quinic, cyclohexanecarboxylic and non-phenolic aromatic acids to benzoic acid.

1. The contribution of dietary constituents to the large urinary output of benzoic acid characteristic of ruminants and some herbivores is not well understood. 2. Methods for the analysis of quinic, cyclohexanecarboxylic, benzoic, phenylacetic, 3-phenylpropionic and cinnamic acids in urine and in rumen fluids were developed. 3. The urinary output of aromatic acids by sheep given seven-rations was determined: benzoic acid output varied between 2.8 and 7.8 g/d; phenylacetic acid output between 0.16 and 1.3 g/d; cinnamic acid between 0.08 and 0.25 g/d and small amounts of 3-phenylpropionic acid were found in some samples. 4. Increments in urinary aromatic acid excretion were determined when the acids listed in paragraph 2 were infused via rumen or abomasal cannulas. 5. When cyclohexanecarboxylic acid was infused 40% of the dose was excreted as urinary benzoic acid after either route of infusion. Quinic acid was completely metabolized in the rumen; following rumen infusion between 16 and 53% of the infused acid was recovered as urinary benzoic acid; none was so recovered after abomasal infusion. 6. Urinary recoveries of rumen- and abomasally-infused aromatic acids were: benzoic acid 90 and 88% respectively as benzoic acid, phenylacetic acid 78 and 83% respectively as phenylacetic acid, 3-phenylpropionic acid 96 and 105% respectively as benzoic acid and cinnamic acid, 70 and 70% respectively as benzoic acid. 7. The concentration of aromatic acids in rumen fluid varied with time after feeding: cyclohexanecarboxylic acid was maximal (7 mg/l) 1 h after feeding, benzoic acid was always a minor component (0.5 +/- 0.5 mg/l), phenylacetic acid varied between 0 and 35 mg/l and 3-phenylpropionic acid between 25 and 47 mg/l. Cinnamic acid was not found in rumen fluid but on rumen infusion of this acid the concentration of 3-phenylpropionic acid in rumen fluid increased by 10 mg/l rumen fluid per g infused per d. 8. The incomplete metabolism of quinic and cyclohexanecarboxylic acids to urinary benzoic acid is discussed. It is concluded that the principal dietary precursors of urinary benzoic acid in ruminants are compounds yielding 3-phenylpropionic acid on microbial fermentation in the rumen. The small amount of cinnamic acid characteristic of ruminant urine arises as an intermediate in the beta-oxidation of 3-phenylpropionic acid in the body tissues.

Animal Feed↗
PubMed1989

Effects of butyric acid and analogues on amylase release from pancreatic segments of sheep and goats.

The specificity of the structural elements of a short-chain fatty acid for stimulating amylase release was investigated in superfused pancreatic segments of sheep and goats in vitro using butyric acid and analogues. Monocarboxylic (cyclohexanecarboxylic and benzoic) acids were as effective as butyric acid, whilst 4-phenyl-n-butyric and dicarboxylic (succinic and phthalic) acids were weak stimulants. The amylase release evoked by butyric acid was markedly reduced in the presence of these compounds. Replacement of hydrogens by a hydroxyl group or amino group or reduction of the carboxyl group to alcohol diminished, while replacement of hydrogen by chloride at the 3 carbon position did not change, the ability to stimulate amylase release. The dose-response curve for butyric acid was shifted to the right in parallel in the solution containing succinic acid at 8 x 10(-4) mol/l. The maximal increment (but not ED50) of amylase release evoked by ACh was severely reduced in the solution simultaneously containing butyric acid at 10(-3) mol/l. These results suggest that short-chain fatty acids are required to possess both carboxyl (hydrophilic) group and hydrophobic tails in order to have the ability to stimulate amylase release, and that amylase release evoked by butyrate is caused through specific recognizing sites for short-chain fatty acids which might be different from ACh receptors, in the pancreatic segments of sheep and goats.

Acetylcholine↗
PubMed1992

Hawkinsinuria in two families.

Hawkinsinuria, a disorder of tyrosine metabolism has been documented in two families in the United States, in one of which there was clear evidence of autosomal dominant inheritance. Metabolic acidosis and failure to thrive appear to be confined to infancy. Tyrosyl metabolites and 5-oxoproline are also found only in infancy, while 4-hydroxycyclohexylacetic acid was present only with time. The disease may be detected by organic acid analysis or by staining an electropherogram for sulfur containing compounds.

Acidosis↗
PubMed1989

In vitro localization of the protein synthesis defect associated with experimental phenylketonuria.

We have used a cell-free system derived from hamster brain to investigate protein synthesis during experimental phenylketonuria. In such a system the elongation inhibitor emetine impeded translation in extracts derived from both treated and control animals. On the other hand the initiation inhibitor aurintricarboxylic acid showed no effects on protein synthesis activity of treated hamsters, although it was severely inhibiting in controls. This suggests that initiation is the altered step in brain protein synthesis failure consecutive to phenylketonuria.

Animals↗
PubMed1985

Inhibition of chlorophyll synthesis in Hordeum vulgare by 3-amino 2,3-dihydrobenzoic acid (gabaculin).

Gabaculin (3-amino 2,3-dihydrobenzoic acid) is shown to be a very potent inhibitor of chlorophyll formation in Hordeum vulgare. Exposure of leaf segments to 30 microM gabaculin results in an 80% inhibition of chlorophyll synthesis, and this is paralleled by a decrease in carotenoid. Dual-inhibitor studies with dioxoheptanoic acid, which is an inhibitor of delta-amino-laevulinic acid dehydratase, show that gabaculin inhibits an earlier step than dioxoheptanoic acid and affects delta-amino-laevulinic acid synthesis rather than its subsequent metabolism.

Aminolevulinic Acid↗
PubMed1979

Dopamine-dependent hyperactivity in the rat following manipulation of GABA mechanisms in the region of the nucleus accumbens.

The effect of manipulation of GABA mechanisms in the region of the nucleus accumbens on dopamine-dependent locomotor hyperactivity in the rat has been studied. Two models of hyperactivity were used: (1) the injection of dopamine into the region of the nucleus accumbens in nialamide-pretreated animals and (2) the systemic administration of d-amphetamine. Both GABA and the GABA agonist 3-aminopropane sulphonic acid (3-APS) depressed hyperactivity in a dose-related manner. High concentrations of GABA (greater than 100 micrograms) were required to produce a significant effect and the response was short-lived possibly reflecting the efficient GABA inactivating mechanisms. 3-APS proved to be approximately 10 times more potent as compared to GABA in the dopamine-accumbens hyperactivity model. Conversely GABA receptor antagonism with low doses of either picrotoxin or bicuculline enhanced the mild locomotor response induced by a low dose of dopamine injected into the nucleus accumbens. However such results were difficult to evaluate fairly as higher doses of the GABA antagonists resulted in varying degrees of generalized seizures. Blockade of GABA uptake systems with cis-1, 3-aminocyclohexane carboxylic acid (ACHC), nipecotic acid or beta-alanine within the region of the nucleus accumbens produced dose-related depression of dopamine-dependent hyperactivity in both models. GABA uptake blockade (nipecotic acid) significantly enhanced the GABA-mediated depression of hyperactivity induced by bilateral injection of dopamine into the nucleus accumbens. The results demonstrate an inhibitory action of GABA and drugs facilitating GABA-ergic transmission on dopamine-dependent hyperactivity in the rat. Although open to criticisms of not being able to distinguish between true GABA effects and the results of non-specific neuronal depression the hyperactivity model underlines the potency of the GABA uptake blocking compounds and their possible potential for future clinical use.

Amino Acids↗
PubMed1983

Synthesis and separation of tritium-labeled intermediates of the shikimate pathway.

[5-3H]Shikimate (sp radioact 2000 Ci/mol) has been synthesized by reduction of the methyl ester of 5-dehydroshikimate with NaB3H4 and subsequent hydrolysis of the ester group (M. M. Leduc, P. M. Dansette, and R. G. Azerad (1970) Eur. J. Biochem. 15, 428-435). The [5-3H]shikimate has been converted enzymatically to [5-3H]chorismate and [5-3H]prephenate of similar high specific radioactivity by using a cell-free extract of Aerobacter aerogenes 62-1. In addition, a chromatographic procedure, which utilizes polyethyleneimine-cellulose thin-layer chromatograms, has been developed for the separation of intermediates along the shikimate pathway between shikimate and hydroxyphenylpyruvate or phenylpyruvate. Since the method allows quantitative measurement of tritium-labeled intermediates, it provides the basis for sensitive radioassays of the individual enzymes and allows study of the reaction flux along the overall pathway. The same intermediates can be separated on a large scale by use of a column of DEAE-Sephacel.

Chorismic Acid↗
PubMed1991

Separation and partial characterization of enzymes catalyzing delta-aminolevulinic acid formation in Synechocystis sp. PCC 6803.

Formation of the universal tetrapyrrole precursor, delta-aminolevulinic acid (ALA), from glutamate via the five-carbon pathway requires three enzymes: glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde (GSA) aminotransferase. All three enzymes were separated from extracts of the unicellular cyanobacterium Synechocystis sp. PCC 6803, and two of them, glutamyl-tRNA synthetase and GSA aminotransferase, were partially characterized. After an initial high speed centrifugation and differentiatial ammonium sulfate fractionation of cell extract, the enzymes were separated by successive affinity chromatography on Reactive Blue 2-Sepharose and 2',5'-ADP-agarose. All three enzyme fractions were required to reconstitute ALA formation from glutamate. The apparent native molecular masses of glutamyl-tRNA synthetase and GSA aminotransferase were determined by gel filtration chromatography to be 63 and 98 kDa, respectively. Neither glutamyl-tRNA synthetase nor GSA aminotransferase activity was affected by hemin concentrations up to 10 and 30 microM, respectively, and neither activity was affected by protochlorophyllide concentrations up to 2 microM. GSA aminotransferase was inhibited 50% by 0.5 microM gabaculine. The gabaculine inhibition was reversible for up to 1 h after its addition, if the gabaculine was removed by gel filtration before the enzyme was incubated with substrate. However, irreversible inactivation was obtained by preincubating the enzyme at 30 degrees C either for several hours with gabaculine alone or for a few minutes with both gabaculine and GSA. Neither pyridoxal phosphate nor pyridoxamine phosphate significantly affected the activity of GSA aminotransferase at physiologically relevant concentrations, and neither of these compounds reactivated the gabaculine-inactivated enzyme. It was noted that the presence of pyridoxamine phosphate in the ALA assay mixture produced a false positive color reaction even in the absence of enzyme.

Aldehyde Oxidoreductases↗
PubMed1985

Abscisic acid increases lipid bilayer permeability to cations as studied by phosphorus-31 NMR.

Using a 31P-NMR lanthanide shift technique, abscisic acid is shown to enhance the permeability to praeseodymium of lipid bilayers composed of 80 mol% phosphatidylcholine and 20 mol% phosphatidylethanolamine. Praeseodymium permeability is immeasurably slow in the absence of the hormone whether or not phosphatidylethanolamine is present in the bilayers. Only in the presence of abscisic acid is praeseodymium permeability observed, the effect being significantly greater when phosphatidylethanolamine is present. These results substantiate prior reports from nonelectrolyte permeability studies that abscisic acid interacts with phosphatidylethanolamine in lipid bilayers.

Abscisic Acid↗
PubMed1985

Modulation of DNA binding of glucocorticoid receptor by aurintricarboxylic acid.

Effects of aurintricarboxylic acid (ATA) were examined on the DNA binding properties of rat liver glucocorticoid-receptor complex. The DNA-cellulose binding capacity of the glucocorticoid-receptor complex was completely abolished by a pretreatment of receptor preparation with 0.1-0.5 mM ATA at 4 degrees C. The half-maximal inhibition (i.d.50) in the DNA binding of [3H]triamcinolone acetonide-receptor complex [( 3H]TARc) was observed at 130- and 40 microM ATA depending upon whether the inhibitor was added prior to or following the receptor activation. The entire DNA-cellulose bound [3H]TARc could be extracted in a concentration-dependent manner by incubation with 2-100 microns ATA. The [3H]TARc remained intact under the above conditions, the receptor in both control and ATA-treated preparations sedimented in the same region in salt-containing 5-20% sucrose gradients. The action of ATA appeared to be on the receptor and not on DNA-cellulose. The DNA-binding capacity of ATA-treated receptor preparations could be recovered upon exhaustive dialysis. The treatment with ATA did not appear to change the ionic behavior of heat activated GRc; the receptor in both control and the ATA-treated preparations showed similar elution profiles. Therefore, ATA appears to alter the binding to and dissociation of glucocorticoid-receptor complex from DNA. The use of ATA should offer a good chemical probe for analysis of the DNA binding domain(s) of the glucocorticoid receptor.

Animals↗
PubMed1988

GABA transaminase inhibitors enhance the release of endogenous GABA but decrease the release of beta-alanine evoked by electrical stimulation of slices of the rat medulla oblongata.

Slices of the rat medulla oblongata were superfused and electrically stimulated. The amount of endogenous GABA, beta-alanine and glutamate release from the slices was determined by high performance liquid chromatography with fluorometric detection. Inhibitors of GABA-transaminase (GABA-T), aminooxyacetic acid (10(-5) M), gamma-acetylenic GABA (10(-4) and 10(-3) M) and gabaculine (10(-5) M), enhanced the stimulus-evoked release of GABA and reduced that of beta-alanine, while no change was observed in the release of glutamate. These changes in amino acid release from the slices were accompanied by an increase in the content of GABA and a decrease in that of beta-alanine. The stimulus-evoked release of these amino acids was abolished by Ca2+-deprivation, in either the presence or absence of GABA-T inhibitors. These results suggest a modulatory role of GABA-T for synaptically releasable GABA and involvement of this enzyme in the synthesis of releasable beta-alanine.

4-Aminobutyrate Transaminase↗
PubMed1988

Formation of 5-aminolevulinate via glutamate-1-semialdehyde and 4,5-dioxovalerate with participation of an RNA component in Scenedesmus obliquus mutant C-2A'.

In the yellow mutant C-2A' of the unicellular green alga Scenedesmus obliquus the participation of an RNA species in the conversion of glutamate to 5-aminolevulinate is clearly demonstrated by the fact that RNAase treatment of a soluble enzyme preparation drastically decreases the formation of 5-aminolevulinate. The involvement of 4,5-dioxovalerate in the C5 pathway is demonstrated by the decrease of label in enzymatically formed 5-aminolevulinate from [14C]glutamate by providing an increased unlabelled pool of 4,5-dioxovalerate. Evidence supporting the role of glutamate-1-semialdehyde as an additional intermediate in the reaction sequence is also presented. We propose a new reaction scheme, consistent with the results reported here, for the formation of 5-aminolevulinate via the C5 pathway.

Aminolevulinic Acid↗