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At least 73 records · Page 4Linked to original sources
PubMed1980

Structure-activity studies on an excitatory receptor for glutamate on leech Retzius neurones.

1 Intracellular recordings were made from Retzius cells from the segmental ganglia of Hirudo medicinalis and Haemopis sanguisuga. Glutamate had a direct excitatory effect on the leech Retzius cells. 2 L-Glutamate was 25 times more potent than D-glutamate. 3 L-Glutamate was approximately equipotent with ibotenic acid and 11.2 times more potent than L-aspartic acid. 4 Quisqualic acid and kainic acid were both approximately 100 times more potent than L-glutamate. DL-1-Amino-cis-1-3-dicarboxyclyclopentane was approximately 5 times more potent than L-glutamate, while the trans isomer was 105 times less potent. 5 alpha-NH2-pimelic acid and beta-CH3-glutamic acid reduced the response to L-glutamate. 6 It is suggested that glutamic acid may interact with the Retzius cell glutamate receptor in an extended conformation.

Animals↗
PubMedDate not supplied

[Protein and amino acid digestibility in various sections of the intestines in swine. 3. Amino acid composition of chyme and fecal proteins].

The amino acid composition in the chyme and faecel protein after feeding pigs with different diets is described. It is to be stated that chyme protein cannot necessarily be considered homogenous. Faecal protein shows less considerable variations in its composition and deviates distinctly from the composition of the faecal bacteria. The quota of bacterial crude protein was calculated according to the content of 2,6 diamino pimelic acid. In the chyme protein (end of the ileum) it amounted to approximately 30% and in the faecal protein to approximately 50%.

Amino Acids↗
PubMed1989

Azelaic acid--biochemistry and metabolism.

Medium chain length dicarboxylic acids (DA) from C8 to C13 are competitive inhibitors of tyrosinase in vitro. The introduction of electron acceptor groups or electron donor groups into the 2 and/or the 8 position of the molecule enhances or reduces respectively the inhibitory effects of DA. In addition to tyrosinase, DA can reversibly inhibit thioredoxin reductase, NADPH cytochrome P450 reductase, NADH dehydrogenase, succinic dehydrogenase and H2CoQ-Cytochrome C oxidoreductase. Among DA, azelaic acid (AA, C9 dicarboxylic acid) is extensively used because: 1) it is much cheaper than other DA; 2) it has no apparent toxic or teratogenic or mutagenic effect; 3) when administered perorally to humans, at the same concentrations as the other DA, it reaches much higher serum and urinary concentrations. Serum concentrations and urinary excretion obtained with intravenous or intra-arterial infusions of AA are significantly higher than those achievable by oral administration. Together with AA, variable amounts of its catabolites, mainly pimelic acid, are found in serum and urine, indicating an involvement of mitochondrial beta-oxidative enzymes. Short-lived serum levels of AA follow a single 1 h intravenous infusion, but prolonging the period of infusion with successive doses of similar concentration produces sustained higher levels during the period of administration. These levels are consistent with the concentrations of AA capable of producing a cytotoxic effect on tumoral cells in vitro. AA is capable of crossing the blood-brain barrier: its concentration in the cerebrospinal fluid is normally in the range of 2-5% of the values in the serum.

Animals↗
PubMed2006

A dinuclear lanthanide complex for the recognition of bis(carboxylates): formation of terbium(III) luminescent self-assembly ternary complexes in aqueous solution.

The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.

Journal Article↗
PubMed1975

Glucosamine-labelled envelope proteins of Escherichia coli K-12. I. Electrophoretic studies and partial fractionation of phenol-soluble proteins.

Hydrophobic envelope proteins were extracted by phenol from a glucosamine- and leucine-requiring mutant of Escherichia coli K-12 (E-110). Three protein fractions labelled with D-[1-14C]glucosamine and L-[4,5-3H]leucine were obtained by electrophoretic separation. Envelopes were isolated from cells labelled with D-[1-14C]glucosamine--HCL and acid hydrolyzed. At least 68% of the radioactivity was recovered as glucosamine and glucose with no random distribution of label. Fingerprinting of pronase digests of glucosamine-labelled proteins showed four radioactive spots associated with peptides. The glycoproteins were pronase- and trypsin-sensitive and had apparent molecular weights of 11 000 (fast mobility), 35 000 (intermediate mobility) and 62 000 (slow mobility) as estimated by sodium dodecyl sulfate-polyacrylamide disc electrophoresis. The two heavier fractions were labelled with meso-diamino[1,7-14C2]pimelic acid, while orth[32P]phosphate was not incorporated into any fraction. The glucosamine radioactivity of the fast fraction underwent rapid changes upon a chase with non-radioactive glucosamine. Using a Sephadex LH-20 column, the radioactive proteins were separated from the phenol and subsequently fractionated on a DEAE-cellulose column. The DEAE-cellulose fractions were distinct from each other in the number and composition of protein bands, when analyzed by sodium dodecyl sulfate-polyacrylamide disc electrophoresis. Radioactive bands with intermediate and fast electrophoretic mobilities were found in separate DEAE-cellulose fractions.

Bacterial Proteins↗
PubMed1986

Neurotoxic action of kainic acid in the isolated toad and goldfish retina: II. Mechanism of action.

The specificity and mechanism of the neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). Of 21 compounds tested as potential mimics of KA neurotoxicity in the OPL, only the enantiomers of glutamate and aspartate mimicked KA, inducing a low-level neurotoxic effect at concentrations 5,000-10,000-fold higher than concentrations of KA giving comparable effects. Further, of 22 compounds tested as potential blockers of KA neurotoxicity in the OPL, only D-gamma-glutamylglycine, D,L-alpha-amino pimelic acid, sodium pentobarbital, D,L-alpha-amino adipic acid, L-glutamate, and L-aspartate blocked KA neurotoxicity (IC50 values of 0.1, 0.3, 0.3, 2, 5, and 15 mM, respectively). In ionic substitution experiments, KA-induced vacuolization was found to require sodium and chloride ions but not calcium ions in the extracellular medium. These findings support the hypothesis that KA combines with specific receptors in the membrane of susceptible neurons in the retinal OPL, leading to prolonged opening of membrane channels permeable to sodium and potassium ions. An accompanying equilibrating chloride influx may result in intracellular ion excess, leading to osmotic swelling and vacuolization. The membrane receptors involved in mediating the action of KA in the OPL are likely to be a class of postsynaptic or extrasynaptic glutamate receptor.

Amino Acids↗
PubMed1969

Synthesis of desthiobiotin from 7,8-diaminopelargonic acid in biotin auxotrophs of Escherichia coli K-12.

The synthesis of desthiobiotin from 7,8-diaminopelargonic acid (DAP) was demonstrated in resting cell suspensions of Escherichia coli K-12 bioA mutants under conditions in which the biotin locus was derepressed. The biosynthetically formed desthiobiotin was identified by chromatography, electrophoresis, and by its ability to support the growth of yeast and those E. coli biotin auxotrophs that are blocked earlier in the biotin pathway. Optimal conditions for desthiobiotin synthesis were determined. Desthiobiotin synthetase activity was repressed 67% when partially derepressed resting cells were incubated in the presence of 3 ng of biotin per ml. Serine, bicarbonate, and glucose stimulated desthiobiotin synthesis apparently by acting as sources of CO(2). The results of this study are consistent with an earlier postulated pathway for biotin biosynthesis in E. coli: pimelic acid --> 7-oxo-8-aminopelargonic acid --> DAP --> desthiobiotin --> biotin.

Amino Acids↗
PubMed1968

Synthesis of 7-oxo-8-aminopelargonic acid, a biotin vitamer, in cell-free extracts of Escherichia coli biotin auxotrophs.

The enzymatic synthesis of 7-oxo-8-aminopelargonic acid (7-KAP) from pimelyl-coenzyme A and l-alanine was demonstrated in cell-free extracts of a biotin mutant of Escherichia coli K-12 which excretes only 7-KAP into the growth medium. This biotin vitamer was identified by its chromatographic and electrophoretic properties. The enzyme (7-KAP synthetase) was repressed when the organism was grown in biotin concentrations greater than 0.2 ng/ml. The parent strain and members of other mutant groups that excrete 7-KAP, in addition to other vitamers, also exhibited synthetase activity. A mutant group that failed to excrete 7-KAP was further sub-divided into three groups, one of which lacked synthetase activity. These results are discussed in relation to a previously proposed scheme for biotin biosynthesis in which the formation of 7-KAP is considered the point of entry for pimelic acid into the biotin pathway.

Acyltransferases↗
PubMed1994

Origin of carbon atoms of biotin. 13C-NMR studies on biotin biosynthesis in Escherichia coli.

The origin of the carbon atoms of pimeloyl-CoA, the earliest known precursor in the pathway of de novo biotin biosynthesis in Escherichia coli, was investigated by 13C-NMR spectroscopy. In fermentation of the biotin-overproducing DRK332/pXBA312 strain of Escherichia coli (a repressor mutant carrying a biotin operon fragment in the plasmid), a high dose of L-alanine (8 g/l) stimulated dethiobiotin and biotin accumulation. Although L-alanine is a known precursor of 7-keto-8-aminopelargonic acid in biotin biosynthesis, the 13C-NMR spectrum of dethiobiotin showed that the C-3 of L-[3-13C]alanine was incorporated into not only the methyl carbon (C-9) but also alternate carbons (C-2, C-4, C-6) of the side chain, and these latter positions are the same as those labeled with D-[1-13C]glucose. These data indicate that L-alanine can act as an alternative carbon source, suggesting that acetyl-CoA is a possible precursor for pimeloyl-CoA synthesis. In accordance with this hypothesis, the C-1 of sodium (1-13C)acetate and the C-2 of sodium (2-13C)acetate were incorporated into alternate carbons in the side chain of dethiobiotin, i.e., (C-1, C-3, C-5, C-7) and (C-1, C-2, C-4, C-6), respectively. These results suggested firstly that in E. coli pimeloyl-CoA is biosynthesized from L-alanine and/or acetate via acetyl-CoA, but not via pimelic acid, which has been suggested as a biotin precursor in other species, and secondly that the carboxyl group of biotin originates from carbon dioxide produced through the tricarboxylic acid cycle.

Acetates↗
PubMed1984

[Effect of guar flour on endogenous nitrogen excretion in rats determined by the 15N-tracer technic].

The metabolic fecal nitrogen was determined in 8 young rats (90-100 g body weight) using a single oral dose of 75 mg 15N-glycine. Four rats were fed a diet containing 8% guar and 4 rats received a control diet without guar. Compared to the control group, apparent protein digestibility and nitrogen balance were significantly lower in the guar group. After an initial steep rise the 15N-elimination in feces and urine (days 2-8 after 15N-glycine application) followed an exponential curve in at least 2 phases, with increasing half-time values. The proportion of metabolic fecal nitrogen to total fecal nitrogen was calculated from the 15N-atom-% excess, determined daily in urine and in feces. This calculation is based on the assumption that the specific 15N-activity (15N-atom-% excess) in urine represents the specific 15N-activity of the endogenous nitrogen pool. The addition of guar raised the proportion of metabolic fecal nitrogen from 51% (control) to 73%, corresponding to an increase in total fecal nitrogen loss (24 mg) observed in the guar-fed animals. This indicates that the rise in fecal nitrogen loss caused by guar is due almost entirely to enhanced secretion of endogenous nitrogen and not to undigested food protein. Based on the analysis of 2,6-diamino-pimelic acid in the feces of 4 rats the proportion of bacterial nitrogen in the feces was calculated. It amounted to 19.8% of total fecal N in the control group, and to 30.1% in the guar group, or to 39.4% and 44.4% of metabolic fecal nitrogen respectively. Obviously the increased dietary fiber intake also caused a rise in the amount of metabolic fecal nitrogen, which is derived from gastro-intestinal secretions and epithelial tissue.

Animals↗
PubMed1984

[Determination of fecal bacterial nitrogen in rats].

A simple method is described by which the fecal flora of rats has been isolated with high recovery and a high purity grade. Total nitrogen and 2.6-diamino-pimelic acid were determined in the isolated bacteria. From both values a factor was calculated, which permits the estimation of fecal bacterial nitrogen from fecal DAP content. In the feces of rats on a semisynthetic control diet (4% cellulose) this factor was 15.7. Addition of 8% guar (by substitution for starch) resulted in a drastic increase in fecal DAP content thus lowering the factor to 11.5. When the proportion of cellulose in the control diet was raised from 4 to 12%, no change in the factor was observed. This indicates a pronounced effect on the bacterial activity by guar but not by cellulose. It is concluded that the factor used to calculate fecal microbial nitrogen from fecal DAP content is dependent on the kind of dietary fiber ingested.

Amino Acids, Diamino↗
PubMed1986

[The effect of cellulose on endogenous nitrogen excretion in rats, evaluated using N-15 technics].

Metabolic faecal nitrogen excretion was assessed in 8 young rats (90-100 g body weight) following an oral application of 75 mg 15N-glycine (95 atom-% 15N). Four rats received an experimental diet containing 12% cellulose, while a control diet containing 4% cellulose was fed to the remaining 4 animals. The high cellulose content induced a highly significant reduction of the N balance due to a greatly increased urinary N excretion. The metabolic faecal nitrogen was determined by measuring 15N excretion in faeces and urine from day 5 (3) to day 8 following 15N glycine administration. During this time interval 15N elimination follows an exponential curve. Increasing the dietary cellulose content from 4 to 12% produced a rise in metabolic faecal nitrogen from 13.9 to 15.7 mg/day and in total faecal nitrogen from 21.3 to 24.4 mg/day. From these values a mean true protein digestibility of 98% was calculated for both groups of rats, regardless of the difference in dietary cellulose content. The fraction of endogenous faecal nitrogen which is of bacterial origin was determined through the analysis of 2, 6-diamino-pimelic acid (DAP). The added cellulose in the experimental diet caused a rise in faecal DAP from 0.302 to 0.402 mg/day corresponding to an increase of bacterial nitrogen from 5.2 to 6.4 mg/day. Accordingly the observed rise in endogenous faecal nitrogen is largely due to increased bacterial nitrogen.

Animals↗
PubMed1989

A novel biosynthesis of medium chain length alpha-ketodicarboxylic acids in methanogenic archaebacteria.

Gas chromatographic-mass spectrometric analysis on the distribution of alpha-ketodicarboxylic acids in various bacteria determined that alpha-ketoglutarate and alpha-ketoadipate are widely distributed in all the bacteria examined, whereas alpha-ketopimelate and alpha-ketosuberate are found only in the methanogenic archaebacteria. Labeling experiments with stable isotopes indicated that each of these acids arises from alpha-ketoglutarate by repeated alpha-ketoacid chain elongation. The final product in this series of reactions, alpha-ketosuberate, serves in the methanogenic bacteria as the biosynthetic precursor to the 7-mercaptoheptanoic acid portion of 7-mercaptoheptanoylthreonine phosphate, a methanogenic coenzyme.

Adipates↗
PubMed1987

Composition of IgA immune complexes precipitated with polyethylene glycol. A model for isolation and analysis of immune complexes.

Covalently cross-linked large and intermediate-sized IgA oligomers, prepared with IgA anti-dinitrophenyl (DNP) and bis-DNP-pimelic acid ester, were used to examine the ability of different concentrations (3.5%, 5% and 7%, w/v) of polyethylene glycol (PEG) to precipitate IgA immune complexes (IgA-IC). The size of the IgA-IC precipitated with PEG was determined by gradient polyacrylamide gel electrophoresis and quantitative autoradiography. The standard concentration of 3.5% PEG precipitated only a minor fraction (20%) of the IgA-IC. In contrast, 5% and 7% PEG precipitated 45% and 79% of the complexes, respectively. To test the influence of the antigen on the PEG assay. IgA-IC prepared with IgA anti-DNP and DNP conjugates of either bovine serum albumin or Ficoll were also used. Approximately 38% of these IgA-IC were precipitated with 3.5%, PEG. By comparison, the concentration of 5% and 7% PEG precipitated 60% and 76% of the IgA-IC, respectively. Distilled water rather than the standard borate-buffered saline was shown to be the optimal solvent for resolubilization of the PEG precipitates. Serum samples from 22 IgA nephropathy patients and 12 normal donors were tested with 3.5%, 5% and 7% PEG. Only the 7% PEG assay showed a significant difference between patients and controls (P less than 0.001) in the IgA levels of precipitates. Thus, the use of 7% PEG is recommended for the detection, isolation and analysis of large- and intermediate-sized IgA-IC.

Antigen-Antibody Complex↗
PubMed1991

Biotin formation by recombinant strains of Escherichia coli: influence of the host physiology.

Strains of Escherichia coli were transformed with different plasmids bearing the gene clusters bioXWF and bioDAYB isolated from the Gram positive bacterium Bacillus sphaericus. These genes encode for the enzymes involved in the metabolic pathway which synthesizes biotin from the precursor pimelic acid. Transformed E. coli strains were grown in bioreactors to reach a biomass of 18 g l-1 cell dry weight in 1 litre batch culture with substrate feeding and approximately 50 g l-1 in 10 l fed batch culture. Improved yields of total vitamers and biotin formed in these processes were achieved after a comparative analysis of different culture conditions, medium compositions, host strains and expression systems. Production of 27 mg l-1 of biotin and 200 mg l-1 of vitamers was achieved in 1 litre batch culture. Using a 10-1 fed batch process, biotin and vitamer concentrations reached maximum values of 45 mg l-1 and 350 mg l-1, respectively.

Bacillus↗