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At least 379 records · Page 21Linked to original sources
PubMed1997

Streptogramin B biosynthesis in Streptomyces pristinaespiralis and Streptomyces virginiae: molecular characterization of the last structural peptide synthetase gene.

Streptomyces pristinaespiralis and S. virginiae both produce closely related hexadepsipeptide antibiotics of the streptogramin B family. Pristinamycins I and virginiamycins S differ only in the fifth incorporated precursor, di(mono)methylated amine and phenylalanine, respectively. By using degenerate oligonucleotide probes derived from internal sequences of the purified S. pristinaespiralis SnbD and SnbE proteins, the genes from two streptogramin B producers, S. pristinaespiralis and S. virginiae, encoding the peptide synthetase involved in the activation and incorporation of the last four precursors (proline, 4-dimethylparaaminophenylalanine [for pristinamycin I(A)] or phenylalanine [for virginiamycin S], pipecolic acid, and phenylglycine) were cloned. Analysis of the sequence revealed that SnbD and SnbE are encoded by a unique snbDE gene. SnbDE (4,849 amino acids [aa]) contains four amino acid activation domains, four condensation domains, an N-methylation domain, and a C-terminal thioesterase domain. Comparison of the sequences of 55 amino acid-activating modules from different origins confirmed that these sequences contain enough information for the performance of legitimate predictions of their substrate specificity. Partial sequencing (1,993 aa) of the SnbDE protein of S. virginiae allowed comparison of the proline and aromatic acid activation domains of the two species and the identification of coupled frameshift mutations.

Amino Acid Sequence↗
PubMed1983

Role of L-lysine-alpha-ketoglutarate aminotransferase in catabolism of lysine as a nitrogen source for Rhodotorula glutinis.

Wild-type and saccharopine dehydrogenaseless mutant strains of Rhodotorula glutinis grew in minimal medium containing lysine as the sole nitrogen source and simultaneously accumulated, in the culture supernatant, large amounts of a product identified as alpha-aminoadipic-delta-semialdehyde. The saccharopine dehydrogenase and pipecolic acid oxidase levels remained unchanged in wild-type cells grown in the presence of ammonium or lysine as the nitrogen source. Lysine-alpha-ketoglutarate aminotransferase activity was demonstrated in ammonium-grown cells. This activity was depressed in cells grown in the presence of lysine as the sole source of nitrogen.

L-Lysine 6-Transaminase↗
PubMedDate not supplied

Kinetics of binding of [(3)H]glycine to transport proteins in channel catfish brain.

[(3)H]Glycine was observed to bind to channel catfish brain particles in a manner displaying saturation kinetics. The dissociation constant was calculated to be 7.38 +/- 2.11 microM. Though some binding occurred in the absence of Na(+) ions, the presence of such ions stimulated binding in a concentration-dependent manner. Similarly, chloride ions had a stimulatory effect on [(3)H]glycine binding. Several inhibitors of binding were identified, the most effective being beta-alanine, pipecolic acid, 2,3-pyrazine dicarboxylic acid and 3,5-pyrazole dicarboxylic acid. Each is a structural analogue of glycine. Harmaline, a known inhibitor of Na(+) binding, also inhibited glycine binding. A previous study had shown the presence of a sodium-dependent, active uptake system for glycine in synaptosomes derived from catfish brain. The present results suggest that the binding of [(3)H]glycine was to a glycine transporter and that the amino acid functions as a neurotransmitter in this species.

Amino Acid Transport Systems, Neutral↗
PubMed1986

Effect of piperidine and related alicyclic amines on nicotinic and muscarinic agonist binding sites in the mammalian brain.

The effect of piperidine and related alicyclic amines on central nicotinic and muscarinic cholinoceptors was investigated by measuring specific binding of [3H]nicotine and [3H]cismethyldioxolane (CD) in rat cerebral cortical membranes. Piperidine, pyrrolidine, 4-hydroxypiperidine and piperazine at concentrations of 1 microM-30 mM completed dose-dependently with [3H]nicotine and [3H]CD for the binding sites. Among these compounds, piperidine was the most potent competitor of brain [3H]nicotine binding sites. Piperidine and pyrrolidine showed a greater affinity for [3H]nicotine binding sites in the rat cerebral cortex than of [3H]CD binding sites. In contrast, 4-hydroxypiperidine and piperazine displayed approximately 10 times greater affinity for [3H]CD binding sites. Pipecolic acid had little effect on these cholinoceptor agonist binding sites. The inhibitory effect of brain [3H]nicotine binding by piperidine did not differ between brain regions or during development. In addition, there was little difference in the piperidine-induced inhibition of brain [3H]nicotine binding between species such as rat, mouse, guinea-pig and rabbit. Thus, the present study demonstrates a high affinity of piperidine for nicotinic cholinoceptors in the mammalian brain.

Amines↗
PubMed1985

The effects of piperidine and its related substances on blood vessels.

Piperidine is an endogenous active amine. Intravenous or intra-arterial administration of piperidine produced vasodilation in anesthetized dogs. The vasodilative effect of piperidine was inhibited by atropine (0.3 mg/kg, i.v.). In the hind limb perfusion experiment in anesthetized dogs, piperidine produced vasodilation, while it showed no vasorelaxing action in various isolated canine arterial strip preparations. These results suggest that the vasodilation caused by piperidine may be produced through activation of muscarinic receptors and that piperidine may act on smaller resistance blood vessels but not on large conductance vessels. In addition, pipecolic acid and N-methyl piperidine, the respective precursor amino acid and metabolite of piperidine, were almost inactive, but nipecotic acid was 1/4 to 1/10 times as active as piperidine as vasodilators. It is suggested that the non-substituted amine moiety of piperidine is very important for the manifestation of vasodilative activity and that piperidine might play a role in regulation of peripheral vascular circulation.

Animals↗
PubMed1983

In vitro activity of U-57930E against anaerobic bacteria and its comparison with clindamycin, ampicillin, carbenicillin and tetracycline.

The in vitro activity of U-57930E, a pipecolic acid amide of clindamycin, was compared with those of clindamycin, ampicillin, carbenicillin and tetracycline against 321 anaerobic clinical isolates. The MIC (micrograms/ml) of U-57930E that inhibited 95% Bacteroides fragilis, Peptococcus prevotii, B. melaninogenicus and P. asaccharolyticus was 0.0625; 0.03125 for Peptostreptococcus anaerobius, B. vulgatus, Propionibacterium and Peptococcus species. Clindamycin, on the other hand, gave MIC values of 0.5 microgram/ml for B. fragilis, P. prevotii and P. asaccharolyticus, 0.25 for Propionibacterium sp. All strains of Clostridium perfringens were inhibited by 0.5 microgram/ml of U-57930E. Both clindamycin and U-57930E showed similar MIC values for all strains of Fusobacterium nucleatum and Propionibacterium acnes tested. The MIC values for ampicillin, carbenicillin and tetracycline were within the expected range. U-57930E had a 4 approximately 8 fold lower MIC than clindamycin and is significantly active against anaerobic bacteria.

Ampicillin↗
PubMed2000

Design of P1' and P3' residues of trivalent thrombin inhibitors and their crystal structures.

Synthetic bivalent thrombin inhibitors comprise an active site blocking segment, a fibrinogen recognition exosite blocking segment, and a linker connecting these segments. Possible nonpolar interactions of the P1' and P3' residues of the linker with thrombin S1' and S3' subsites, respectively, were identified using the "Methyl Scan" method [Slon-Usakiewicz et al. (1997) Biochemistry 36, 13494-13502]. A series of inhibitors (4-tert-butylbenzenesulfonyl)-Arg-(D-pipecolic acid)-Xaa-Gly-Yaa-Gly-betaAla-Asp-Tyr-Glu-Pro-Ile-Pro-Glu-Glu-Ala- (be ta-cyclohexylalanine)-(D-Glu)-OH, in which nonpolar P1' residue Xaa or P3' residue Yaa was incorporated, were designed and improved the affinity to thrombin. Substitution of the P3' residue with D-phenylglycine or D-Phe improved the K(i) value to (9.5 +/- 0.6) x 10(-14) or 1.3 +/- 0.5 x 10(-13) M, respectively, compared to that of a reference inhibitor with Gly residues at Xaa and Yaa residues (K(i) = (2.4 +/- 0.5) x 10(-11) M). Similarly, substitution of the P1' residue with L-norleucine or L-beta-(2-thienyl)alanine lowered the K(i) values to (8.2 +/- 0.6) x 10(-14) or (5.1 +/- 0.4) x 10(-14) M, respectively. The linker Gly-Gly-Gly-betaAla of the inhibitors in the previous sentence was simplified with 12-aminododecanoic acid, resulting in further improvement of the K(i) values to (3.8 +/- 0.6) x 10(-14) or (1.7 +/- 0.4) x 10(-14) M, respectively. These K(i) values are equivalent to that of natural hirudin (2.2 x 10(-14) M), yet the size of the synthetic inhibitors (2 kD) is only one-third that of hirudin (7 kD). Two inhibitors, with L-norleucine or L-beta-(2-thienyl)alanine at the P1' residue and the improved linker of 12-aminododecanoic acid, were crystallized in complex with human alpha-thrombin. The crystal structures of these complexes were solved and refined to 2.1 A resolution. The Lys(60F) side chain of thrombin moved significantly and formed a large nonpolar S1' subsite to accommodate the bulky P1' residue.

Amino Acid Sequence↗
PubMed1988

[Effect of antagonists of excitatory amino acids on synaptic transmission in the electroreceptors (Lorenzini's ampullae) in skates].

Ampullae of Lorenzini isolated from the skate (Raja clavata) have been investigated in vitro electrophysiologically to determine the nature of the transmitter at the synapse between the electroreceptor cells and afferent fibres. Glutamic acid diethyl ester (GDEE), glutamic acid dimethyl ester (GDME), kynurenic acid (KENYA), cis-2,3-piperidine dicarboxylic acid (PDA) reversibly decreased the resting and stimulus-induced activity. These antagonists also blocked postsynaptic responses induced by glutamate and aspartate. D-alpha-aminoadipic acid (DAA) had no effect on the afferent activity. These findings suggest that glutamate, aspartate or a related compound may be a transmitter at this synapse. An important physiological role of quisqualate receptors in ampullae of Lorenzini is also inferred from these experiments.

2-Aminoadipic Acid↗
PubMed1988

Cerebrohepatorenal syndrome of Zellweger: a peroxisomal deficiency disorder. Case report and review.

The cerebrohepatorenal syndrome of Zellweger (CHRS) is a rare, fatal disorder in newborn infants. Recent research points to a primary absence of tissue peroxisomes, with resulting biochemical defects, as the basic pathology of the condition. We report on an infant with classic neurological and dysmorphic features of CHRS. Increased serum levels of pipecolic acid, bile acid precursors and very-long-chain fatty acids (VLCFA) together with total histological absence of liver peroxisomes confirmed the diagnosis. To our knowledge, this is the first case in Israel to be fully documented by biochemical and ultrastructural techniques. A high index of suspicion is essential among clinicians if further cases are not to be overlooked.

Facial Bones↗
PubMed1984

[Substitution of antithrombin III by synthetic thrombin inhibitors].

Synthetic, low-molecular weight thrombin inhibitors may substitute for antithrombin III in inactivating thrombin in vitro and in vivo. They are superior to heparin as antithrombotic agents in antithrombin deficiency or consumption. Studies in experimental animals show the effectiveness of synthetic thrombin inhibitors in immunologic antithrombin depletion, thrombin-induced consumption and CCl4-induced liver failure.

Animals↗
PubMed1984

[Diagnosis of Zellweger's cerebrohepatorenal syndrome].

The cerebro-hepato-renal syndrome of Zellweger is an autosomal recessive inborn error of metabolism. Clinically the disease is characterised by craniofacial malformations, a lack of muscle tone, disturbances in liver function, renal cysts and mental retardation. The disease is characterised biochemically by the absence of peroxisomes (microbodies) in liver and kidney and variable abnormalities in mitochondria. This results in elevated concentrations of pipecolic acid and of tri(di)hydroxycoprostanoic acid in urine, CSF and/or duodenal fluid, an elevation of the concentration of very long chain (greater than C22) fatty acids in plasma and fibroblasts and a deficiency of plasmalogens in tissues, erythrocytes and fibroblasts. Moreover, we recently found that in Zellweger patients the activity of dihydroxyacetone phosphate acyltransferase is deficient in tissues, fibroblasts and cultured amniotic fluid cells and that the incorporation of a radioactive precursor of plasmalogens into phospholipids is impaired in fibroblasts and amniocytes. These recent findings allow specific prenatal and postnatal diagnosis of this disease.

Abnormalities, Multiple↗
PubMed1983

[A child with Zellweger's cerebrohepatorenal syndrome].

A child suffering from the cerebro-hepato-renal syndrome of Zellweger is presented. The clinical features are hypotonia, slow or absent feeding, profound psychomotor retardation, severe impairment of hearing, disturbed visual acuity and a characteristic facial appearance including high forehead and large fontanels. The biochemical abnormalities are disturbed liver function tests, increased concentration of pipecolic acid in serum, cerebrospinal fluid and urine, di- and trihydroxycoprostanic acid detectable in bile, serum and urine and an increased excretion of para-hydroxy-phenyllactate in urine.

Abnormalities, Multiple↗
PubMed1980

Cyclic peptides. VII. Synthesis and conformation of diastereomeric analogs of cyl-2 containing L-proline and L-leucine.

Two diastereomeric cyclic tetrapeptides with a sequence of cyclo (-D (and L)-Tyr (me)-L-Ile-L-Pro-L-Leu-) (ID and IL) have been synthesized, which are simplified analogs of a phytotoxic peptide Cyl-2, and contain an L-proline and an L-leucine residue in place of an L-pipecolic acid and a 2-amino-8-oxo-9,10-epoxydecanoic acid residue, respectively, in Cyl-2. The cyclization of the H-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu proceeded smoothly to give ID in excellent yield (50%), but the cyclization of H-L-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu gave IL in much lower yield (10%). Based on the results of 1H- and 13C-n.m.r. studies, differential N-methylation and model buildings of ID, the backbone structure of ID has been proposed to be a unique trans-trans-cis-trans conformation, the L-Ile-L-Pro bond being cis.

Amino Acid Sequence↗