Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMINO ACIDS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed1991

Subsite mapping of an acidic amino acid-specific endopeptidase from Streptomyces griseus, GluSGP, and protease V8.

The substrate specificities of an acidic amino acid-specific endopeptidase of Streptomyces griseus, GluSGP, and protease V8 [EC 3.4.21.19] were investigated with peptide p-nitroanilide substrates which have a Glu residue at the P1 position. GluSGP and protease V8 favored Pro and Leu residues at S2, respectively, while the S3 subsite of GluSGP preferred Phe over either Ala or Leu. The S3 subsite of protease V8 preferred Leu over either Ala or Phe. The best substrates for GluSGP and for protease V8 were Boc-Ala-Phe-Pro-Glu-pNA with a Km value of 0.41 mM (0.1 M Tris-HCl, pH 8.8) and Boc-Ala-Leu-Leu-Glu-pNA with a Km value of 0.25 mM (0.1 M phosphate, pH 7.8), respectively. The kcat/Km values for these substrates obtained with GluSGP were about one hundred to twenty thousand times larger than those obtained with protease V8. Protease V8 exhibited a single optimal pH of around 8 for the hydrolysis of Boc-Ala-Ala-Leu-Glu-pNA and Boc-Ala-Leu-Leu-Asp-pNA.

Amino Acid Sequence↗
PubMed1975

Formation of chromatographically unique species of transfer ribonucleic acid during amino acid starvation of relaxed-control Escherichia coli.

Examination of the transfer ribonucleic acid (tRNA) produced by starving, relaxed-control (rel minus) strains of Escherichia coli for required amino acids revealed the occurrence of a number of chromatographically unique subspecies. Leucine starvation results in the formation of new isoacceptor species of leucine-, histidine-, arginine-, valine-, and phenylalanine-specific tRNA and quantitative changes in the column profiles of serine, glycine, and isoleucine tRNA. Evidence that the unique tRNA species are synthesized de novo during amino acid starvation comes from the findings that the major unique leucine isoacceptor species is not formed in stringent control cells or in rel minus cells starved for uracil or treated with rifampin. Furthermore, heat treatment of the unique leucine tRNA does not alter its chromatographic behavior, indicating that the species is not an aggregate or nuclease-damaged form of a normal isoacceptor tRNA. The methyl acceptor activities of tRNA from leucine-starved and nonstarved rel+ or rel minus cells were found to be essentially the same. This result and the finding that the chromatographic behavior of the unique leucine-specific tRNA was not altered after treatment with tRNA methylase suggests that gross methyl deficiency is probably not the biochemical basis for the occurrence of the unique species.

Acylation↗
PubMed1983

Kynurenic acid inhibits synaptic and acidic amino acid-induced responses in the rat hippocampus and spinal cord.

Kynurenic acid, a tryptophan metabolite, inhibits excitatory synaptic transmission in the rat hippocampal slice and the isolated immature rat spinal cord, but does not affect membrane potential or input resistance of hippocampal CA1 pyramidal cells. Kynurenic acid also antagonizes responses induced in the dentate gyrus by excitatory amino acids, particularly N-methyl-DL-aspartate and the endogenous excitant quinolinic acid. These results indicate that kynurenic acid antagonizes synaptic transmission probably by blocking postsynaptic transmitter receptors at putative amino acid mediated synapses.

Amino Acids↗
PubMed1993

Primary structure of the murine monoclonal IgG2a antibody mAb735 against alpha (2-8) polysialic acid. 2. Amino acid sequence of the heavy (H-) chain Fd' region.

The complete amino acid sequence of the Fd' region including the VH part, the CH1 domain, and the hinge segment of the biologically relevant monoclonal mouse anti-alpha (2-8) polysialic acid antibody mAb735 is presented. The reduced and carboxymethylated H-chain was digested with trypsin and cyanogen bromide. For subfragmentation selected peptides were cleaved with thermolysin and endoproteinase Asp-N. The generated peptides were isolated by RP-HPLC and characterized by sequence analysis, plasma desorption mass spectrometry (PDMS), and amino acid analysis. The N-terminal sequence was determined after enzymatic deprotection with pyroglutamate aminopeptidase. According to Kabat et al. the variable region of the H-chain belongs to the subgroup II. Sequence data from the constant region indicate that mAb735 represents the gamma 2a isotype.

Amino Acid Sequence↗
PubMed2005

Quantification of indole-3-acetic acid and amino acid conjugates in rice by liquid chromatography-electrospray ionization-tandem mass spectrometry.

A method for quantifying indole-3-acetic acid (IAA) and its conjugates with the six amino acids, Ala, -Asp, -Ile, -Glu, -Phe and -Val, in rice (Oryza sativa) by using high-performance liquid chromatography coupled with electrospray ionization and tandem mass spectrometry (HPLC-ESI-MS/MS) is described. Samples from the rice plant or callus were treated with 80% acetone in water containing 2.5 mM diethyl dithiocarbamate. Each extract was partially purified in C18 cartridge column for solid-phase extraction (SPE) and subjected to HPLC-ESI-MS/MS without converting the product. The detection limit was 3.8 fmol for IAA, and 0.4-2.9 fmol for the IAA amino acid conjugates. The method was applied to the analysis of IAA and its conjugates in rice seedlings, dehulled rice and calli, using 20-100 mg tissue samples.

Amino Acids↗
PubMed1975

[Relations between structure and bitter taste of amino acids and peptides. I. Amino acids and related compounds].

About 60 amino acids, amino acid esters, N-acyl amino acids, amines, and other related compounds were tested for bitter taste. The recognition thresholds are in the range from 100 muMol/ml (L-2-amino butyric acid) to 0.8 muMol/ml (benzamide). Essential structural requirements for bitter compounds are a polar (electrophilic) group and a hydrophobic one, which must be arranged in a defined manner. The results are summarized in a model which shows the zones of contact between bitter compound and receptor.

Amino Acids↗
PubMed1989

Neuronal activity, amino acid concentration and amino acid release in the substantia nigra of the rat after sodium valproate.

The effects of sodium valproate on extracellularly recorded spontaneous neuronal activity and striatal-evoked inhibition in the substantia nigra zona reticulata of the rat were compared with its effects on the tissue concentration of endogenous amino acids and their spontaneous release into perfusates of this region obtained with a push-pull cannula. Valproate (200 mg/kg i.p.) produced a rapid and sustained reduction in the firing rate of all reticulata neurones tested and a concomitant increase in the duration of striatal-evoked inhibition. No change in the spontaneous release of any amino acid was observed. A significant elevation of nigral gamma-aminobutyric acid concentration was seen in both anaesthetized and non-anaesthetized animals, but this occurred only after 60 minutes. Valproate produced a rapid decline in nigral aspartate in non-anaesthetized but not in anaesthetized animals. The results of this study suggest that the acute depressant effect of valproate is unrelated to its ability to alter the concentration of GABA or aspartate in brain and is most likely due to a postsynaptic action.

Action Potentials↗
PubMed1987

High-performance liquid chromatography of phenylthiocarbamyl derivatives of amino acids and side-chain derivatized amino acids.

Amino acid analysis by precolumn derivatization with phenyl isothiocyanate and subsequent characterization of the phenylthiocarbamyl derivatives by high-performance liquid chromatography on an inexpensive Supersphere C8 column is described. The phenylthiocarbamyl derivatives of common amino acids from protein hydrolysates are separated within 15 min. Suggestions for optimization of the system with respect to the separation of closely eluting derivatives are given. The characterization of side-chain-derivatized, e.g., phosphorylated and sulphated amino acids and of a series of biologically active amino acid analogues is described.

Amino Acids↗
PubMed1980

Human fibroblast interferon: amino acid analysis and amino terminal amino acid sequence.

The purification of human fibroblast interferon has been simplified to a two-step procedure consisting of affinity chromatography on Blue Sepharose and sodium dodecyl sulfate polyacrlamide gel electrophoresis. A preliminary amino acid composition and the sequence of the 13 amino-terminal residues of homogeneous interferon prepared by this method is reported.

Amino Acid Sequence↗
PubMed1976

Acid-labile amino acid precursors in the Murchison meteorite. II: A search for peptides and amino acyl amides.

The basic fraction of the acid-labile amino acid precursors found in hot water extracts of the Murchison meteorite was treated with ninhydrin under conditions that give destruction of free amino acids but allow nearly complete recovery to peptides and amino acylamides. After this treatment and a subsequent acid hydrolysis, the amount of amino acids found corresponded to less than 30 per cent of the precursor content of the basic fraction. Since only 30 percent of the total extract precursors are found in the basic fraction, these results indicate that such compounds, if present, account for no more than 9 mole per cent of the total acid-labile amino acid precursors of the meteorite hot water extract.

Amides↗
PubMed1994

Fatty acid and amino acid composition in haruan as a potential role in wound healing.

1. Two species of snakehead fish are available in Sabah, i.e. Channa striatus and Channa melanosoma, and are commonly known as haruan. Haruan is consumed by many Malaysians to induce healing after a clinical operations. However, there is no scientific evidence as yet to substantiate the claim, and so it was decided to analyse the biochemical composition in haruan to determine which compounds may have a possible role or potential in wound healing. 2. Samples (midline fillet) of both species were extracted separately in hexane for the qualitative analysis of fatty acids by a gas chromatography, Hewlett-Packard 5890A, using a 10 meter superox 11 column (Alltech) at temperature between 190 and 245 degrees C. Peak areas were calculated automatically using Hewlett-Packard 3393A computing integrator. Subsequently, the amino acid composition was analysed using a precolumn derivatization reverse phase HPLC waters PICO-TAG system. 3. Haruan is found to contain unusually high arachidonic acid (AA) but almost no eicosapentaenoic acid (EPA). AA which is a precursor of prostaglandin may initiate blood clotting and be responsible for growth. Haruan also contains all the essential amino acids for wound healing, particularly glycine which is the most important component of human skin collagen. Therefore, haruan contained all the basic biochemical requirements for wound healing.

Amino Acids↗
PubMedDate not supplied

Effect of glucose and/or branched chain amino acid infusion on plasma amino acid imbalance in chronic liver failure.

The characteristic amino acid pattern observed in chronic liver failure with high aromatic and low branched chain amino acid levels is considered to be consequent to increased muscle protein catabolism. The main catabolic stimulus has been attributed to hyperglucagonemia and to a reduced insulin/glucagon molar ratio. Intravenous administration of a solution containing branched chain amino acids and glucose to patients with chronic liver cirrhosis rapidly normalizes the plasma amino acid pattern. This effect may result from either a change in the insulin/glucagon ratio, induced by glucose, or from the anticatabolic influence of branched chain amino acids on muscle protein turnover. To discriminate between these two possibilities, a crossover study was carried out to determine the effect of a 24-hour infusion of either glucose alone, or glucose plus branched chain amino acids, in seven patients with chronic liver failure. Blood glucose, insulin, glucagon, free fatty acids, and amino acid levels were determined. Branched chain amino acids were much more effective than glucose (p less than 0.01) in decreasing the levels of aromatic amino acids. Conversely, the insulin, glucagon, and free fatty acid levels with glucose alone were not altered with the addition of branched chain amino acids. These findings suggest an anticatabolic effect of branched chain amino acids on muscle protein turnover and suggest that factors other than insulin and glucagon may be responsible for the characteristic plasma amino acid pattern present in chronic liver failure.

Adult↗
PubMed1976

Plasma amino acids in reptiles after feeding protein or amino acids and after injecting amino acids.

Turtles (Pseudemys scripta elegans) and alligators (Alligator mississipiensis) were fed fish, casein, or free amino acid mixtures, or were injected with free amino acid mixtures, quantities in each case being equivalent to about 42 mmoles of amino acids/kg body weight. The experiments were designed to determine whether protein synthesis normally precedes catabolism of the amino acids absorbed from digesting food. Both animals disposed of free or food-derived amino acids more rapidly than could be accounted for by catabolism alone, but the transient increases in turtle plasma concentrations consisted mostly of essential amino acids, whereas the alligator plasma showed little increase in essential amino acids and considerable rises in four nonessential amino acids, glutamine, glutamic acid, glycine and alanine. Despite some species variation, these two species with low metabolic rates apparently utilized protein synthesis to dispose of amino acid mixtures prior to the necessarily slow process of catabolism for energy.

Administration, Oral↗
PubMed1999

The role of glucose, long-chain triglycerides and amino acids for promotion of amino acid balance across peripheral tissues in man.

The role of amino acids, glucose and lipids in improving amino acid balance in peripheral tissues was evaluated. Primed constant infusion of L-[ring-2H5]phenylalanine in combination with flux measurements of glucose, free fatty acids (FFA) and amino acids across arm and leg tissues were applied in male volunteers after an overnight fast with subsequent primed constant infusions of amino acids (0.2 g N kg-1 body weight day-1), long-chain triglycerides (0.98-1.079 g kg-1 day-1) and glucose (3.13-3.62 g kg-1 day-1). Amino acids and phenylalanine tracer infusion continued for 6 h; the lipid infusion was provided during 2-6 h from the start, and glucose infusion was provided between 4 and 6 h. Flux measurements were performed at steady state before the next infusion started. Arterial concentrations of infused substrates increased during provision, but remained constant thereafter. Plasma insulin increased when glucose was provided, whereas insulin-like growth factor (IGF) I was unchanged during all infusions. Blood flow was unchanged in arm tissue during all infusions, while leg blood flow increased during fat and glucose infusion. FFA and glucose balance were unchanged during amino acid infusion but improved during lipid and glucose infusions. Amino acid balance was negative across arm and leg tissues in the fasted state, but reached balance during amino acid infusion. This effect was equally dependent on protein synthesis and protein degradation without any contribution from lipids and glucose. 3-Methylhistidine release from tissues was not influenced by any substrate. Our results suggest that extracellular amino acid concentrations determine amino acid balance across peripheral tissues independently of non-protein calories, insulin and IGF-I.

Adult↗
PubMed2006

Determination of enantiomeric excess and concentration of unprotected amino acids, amines, amino alcohols, and carboxylic acids by competitive binding assays with a chiral scandium complex.

A practical UV-vis sensing method for enantioselective microanalysis of unprotected amino acids, amines, amino alcohols, and carboxylic acids in aqueous solution has been developed. Both concentration and enantiomeric composition of a wide range of chiral substrates can be determined with high accuracy by two simple competitive binding assays using a scandium complex derived from 1,8-bis(3-(3',5'-dimethylphenyl)-9-acridyl)naphthalene N,N'-dioxide.

Amines↗
PubMedDate not supplied

Epinephrine transiently increases amino acid disappearance to lower amino acid levels in humans.

BACKGROUND: Infusion of epinephrine decreases plasma amino acid concentrations. However, the mechanism by which this decrement occurs is not well characterized. METHODS: Epinephrine was infused (40 ng/kg/min) for 2 hours into eight normal healthy adults. The essential amino acid tracers L-[1-(13)C]leucine and L-[phenyl-2H5]phenylalanine were infused before and during the epinephrine infusion and blood samples obtained to determine amino acid rates of appearance and disappearance from the time course of change in amino acid concentration and tracer enrichments. RESULTS: Epinephrine infusion decreased plasma leucine and phenylalanine concentrations over a period of 30 to 90 minutes after the start of the epinephrine infusion. Epinephrine infusion induced an immediate decrement in tracer enrichments. These changes defined sharp increases in both rate of appearance and rate of disappearance. By 30 minutes of epinephrine infusion, the rate of amino acid appearance from proteolysis had returned to baseline, but the rate of amino acid disappearance remained elevated for 90 minutes before returning to baseline. It was the protracted increase in amino acid disappearance that was responsible for the lowering of plasma amino acid concentrations. After this acute response, rates of amino acid appearance and disappearance returned to normal whereas plasma amino acid levels remained suppressed. CONCLUSIONS: Epinephrine transiently affects both rates of amino acid appearance and disappearance, with the net effect being increased in amino acid disappearance. However, epinephrine lowers amino acid concentrations beyond the period that it affects kinetics. These results suggest that the effect of epinephrine on amino acid metabolism is not detrimental and that epinephrine allows amino acid metabolism to proceed normally but at lower concentrations of amino acids.

Adult↗