scholarly journals NEW MUTATIONAL VARIANTS OF NEUROSPORA NADP-SPECIFIC GLUTAMATE DEHYDROGENASE

Genetics ◽  
1980 ◽  
Vol 95 (2) ◽  
pp. 305-316
Author(s):  
John A Kinsey ◽  
J R S Fincham ◽  
M A M Siddig ◽  
Margaret Keighren
Keyword(s):  
Amino Acid ◽  
Glutamate Dehydrogenase ◽  
The Other ◽  
Tryptophan Residue ◽  
High Concentrations ◽  
Very High

ABSTRACT The am locus of Neurospora codes for NADP-dependent glutamate dehydrogenase (GDH). Four new am mutants that produced mutationally altered GDH have been characterized. Mutant am  119 is a CRM-negative, complementing mutant that maps between am  2 and am  1. The other three mutants are CRM formers that produce varieties of GDH that can be activated by glutamate or succinate. The GDH of am  130 and am  l31 is similar in terms of activation properties to that of am  3. The GDH of am  l22, requires very high concentrations of dicarboxylate for activity. The mutation in am  l30 maps between am  l4 and am  2 and resulted in a replacement at residue 75 of the GDH (pro→ser). The mutation in am  l22 maps near am  ll and apparently resulted in the replacement of the tryptophan residue at position 389 with an unknown amino acid. The mutation in am  l31 maps between am  2 and am  1.

Allosteric behaviour of 1:5 hybrids of mutant subunits of Clostridium symbiosum glutamate dehydrogenase differing in their amino acid specificity

2001 ◽  
Vol 360 (3) ◽  
pp. 651-656 ◽  
Author(s):  
Arun GOYAL ◽  
Xing-Guo WANG ◽  
Paul C. ENGEL
Keyword(s):  
Amino Acid ◽  
Glutamate Dehydrogenase ◽  
Cysteine Residue ◽  
The Other ◽  
Wild Type Enzyme ◽  
Triple Mutant ◽  
Subunit Stoichiometry ◽  
Clostridium Symbiosum ◽  
Mutant Forms ◽  
Fold Activation

Hybrid hexamers were made by refolding mixtures of two mutant forms of clostridial glutamate dehydrogenase. Mutant Cys320Ser (C320S) has a similar activity to the wild-type enzyme, but is unreactive with Ellman's reagent, 5,5′-dithiobis(2-nitrobenzoate) (DTNB). The triple mutant Lys89Leu/Ala163Gly/Ser380Ala (K89L/A163G/S380A), active with norleucine but not glutamate, is inactivated by DTNB, since the amino acid residue at position 320 is a cysteine residue. The chosen ratio favoured 1:5 hybrids of the triple mutant and C320S. The renatured mixture was treated with DTNB and separated on an NAD+–agarose column to which only C320S subunits bind tightly. Fractions were monitored for glutamate and norleucine activity and for releasable thionitrobenzoate to establish subunit stoichiometry. A fraction highly enriched in the 1:5 hybrid was identified. Homohexamers (C320S with 40mM glutamate and 1mM NAD+ at pH8.8, or K89L/A163G/S380A with 70mM norleucine and 1mM NAD+ at pH8.5) showed allosteric activation; succinate activated C320S approx. 50-fold (EC50 = 70mM, h = 2.4), and glutarate gave approx. 30-fold activation (EC50 = 35mM, h = 2.3). For the triple mutant, corresponding values were 80mM and 2.2 for succinate, and 75mM and 1.7 for glutarate, but maximal activation was only about 2-fold. In the 1:5 hybrid, with only one norleucine-active subunit per hexamer, responses to glutarate and succinate were still co-operative, and activation was more extensive than in the triple mutant homohexamer. A single norleucine-active subunit can thus respond co-operatively to a substrate analogue at the other five inactive sites. On the other hand, similar hyperbolic dependence on the norleucine concentration for the hybrid and the triple mutant homohexamer reflected the inability of C320S subunits to bind norleucine. With glutamate at pH8.8, an h value of 3.6 was obtained for the 1:5 hybrid, in contrast with an h value of 5.2 for the C320S homohexamer. The ‘foreign’ subunit evidently impedes inter-subunit communication to some extent.

ACETYLASPARTIC ACID AND AMMONIA POISONING

1960 ◽  
Vol 38 (7) ◽  
pp. 763-768 ◽  
Author(s):  
Jean-Paul Du Ruisseau
Keyword(s):  
Amino Acid ◽  
Ammonium Acetate ◽  
Normal Liver ◽  
The Other ◽  
Normal Brain ◽  
High Concentrations ◽  
The One ◽  
Ammonia Poisoning

Acetylaspartic acid has been followed in nine tissues of normal and ammonia-poisoned rats. This acetylated amino acid is present at high concentrations in normal brain and remains unchanged in ammonia-poisoned brain. Acetylaspartic acid is absent or present in trace amounts in normal liver. It increases appreciably in ammonium acetate poisoning, reaching a peak at death. No change in concentration was detectable in the other tissues examined. There is a correlation between aspartic and acetylaspartic acid in the liver. But no correlation was observed between acetylaspartic acid on the one hand and ammonia and urea on the other. The possible origins of acetylaspartic acid are discussed.

Transport and exchange diffusion of l-tryptophan in Ehrlich cells

1961 ◽  
Vol 200 (5) ◽  
pp. 1063-1068 ◽  
Author(s):  
John A. Jacquez
Keyword(s):  
Amino Acid ◽  
Initial Velocity ◽  
The Other ◽  
Preliminary Loading ◽  
Exchange Diffusion ◽  
Diaminobutyric Acid ◽  
Low Concentrations ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Cells ◽  
High Concentrations

The initial velocity of uptake of l-tryptophan by Ehrlich ascites cells can be explained as the sum of two processes: diffusion and an active transport that shows a saturation effect. Azaserine, l-2,4 diaminobutyric acid, l-histidine, and l-leucine, at low concentrations, increase the initial velocity of uptake of l-tryptophan but compete with l-tryptophan at high concentrations. Preliminary loading of the cells with glycine decreases the initial tryptophan flux: preliminary loading of the ascites cells with azaserine or tryptophan markedly increases the initial flux of uptake of the other amino acid.

Trehalose Protects Yeast Pyrophosphatase against Structural and Functional Damage Induced by Guanidinium Chloride

1996 ◽  
Vol 51 (3-4) ◽  
pp. 160-164 ◽  
Author(s):  
Mauro Sola-Penna ◽  
José Roberto Meyer-Fernandes
Keyword(s):  
Protective Effect ◽  
Degradation Product ◽  
Stress Condition ◽  
Stress Conditions ◽  
The Other ◽  
Guanidinium Chloride ◽  
Nium Chloride ◽  
Pyrophosphatase Activity ◽  
High Concentrations ◽  
Very High

Abstract Trehalose is accumulated at very high concentrations in yeasts when this organism is sub­ mitted to a stress condition. This report approaches the question on the protective effect of trehalose and its degradation product, glucose, against structural and functional damage promoted by guanidinium on yeast cytosolic pyrophosphatase. Here it is shown that both, 1 ᴍ trehalose or 2 ᴍ glucose, are able to attenuate at almost the same extent the conforma­ tional changes promoted by guanidinium chloride on the pyrophosphatase structure. On the other hand, while 1 m trehalose increases 3.8 times the Ki (from 0.15 to 0.57 ᴍ) for guanidi­ nium chloride inhibition of pyrophosphatase activity, 2 m glucose did not even duplicate this parameter (from 0.15 to 0.25 ᴍ). These data support evidences for a functional reason for the accumulation by yeasts of trehalose, and not other compound, during stress conditions.

Contrast Medium Induced Changes in Granulocyte Adherence in Vitro and during Angiography

1988 ◽  
Vol 29 (5) ◽  
pp. 585-588 ◽  
Author(s):  
E. V. Lang ◽  
E. C. Lasser
Keyword(s):  
Contrast Medium ◽  
Human Body ◽  
Indirect Effect ◽  
Femoral Vein ◽  
The Other ◽  
High Concentrations ◽  
Induced Changes ◽  
Very High

The effect of ioxaglate and diatrizoate on per cent granulocyte adherence to nylon fibers was investigated in blood to which contrast medium was added in vitro and in blood from patients undergoing angiography. Very high concentrations of contrast medium, added to blood in vitro, directly abolished granulocyte adherence to nylon fibers. Intraaortic bolus injections of ioxaglate, but not of saline, transiently increased granulocyte concentrations in the femoral vein. Fractional granulocyte adherence to nylon fibers increased significantly above the baseline when angiographic dosages of contrast medium were diluted by circulation within the human body. On the other hand, dilute concentrations of contrast medium had no effect on per cent granulocyte adherence when added to whole blood in vitro. This indicates that the increased adherence produced in vivo is an indirect effect, which, usually, cannot be simulated in vitro.

scholarly journals Comparison of the biliproteins from two strains of the thermophilic cyanophyte Synechococcus lividus

1974 ◽  
Vol 141 (2) ◽  
pp. 419-425 ◽  
Author(s):  
Robert MacColl ◽  
Mercedes R. Edwards ◽  
Martha H. Mulks ◽  
Donald S. Berns
Keyword(s):  
Amino Acid ◽  
Fluorescence Polarization ◽  
Amino Acid Analysis ◽  
Sedimentation Coefficient ◽  
Sedimentation Velocity ◽  
The Other ◽  
Sedimentation Equilibrium ◽  
Temperature Ranges ◽  
Synechococcus Lividus ◽  
Very High

C-Phycocyanins from two thermophilic strains of Synechococcus lividus that grow within different temperature ranges have been shown to be unalike. The aggregation ability of these two C-phycocyanins in sedimentation-velocity experiments varied dramatically. Surprisingly, the aggregation properties of mesophilic C-phycocyanins were found to lie between those of the two thermophilic proteins. Under identical conditions at pH7.0, one thermophilic protein (Sy I) was composed of 17S and larger aggregates, whereas the other (Sy III) was an almost homogeneous 6S aggregate. Mesophilic C-phycocyanins have a mixture of 6S, 11S and less stable 17S aggregates under these conditions. Amino acid analysis, absorption spectra, immunochemistry and fluorescence polarization all indicated differences in the composition and properties of the thermophilic proteins, which suggest that they have different modes of adaptation to very high temperatures. Allophycocyanins from the two strains of S. lividus were also purified and studied, but unlike the C-phycocyanins no major differences were found between them. Allophycocyanin was homogeneous at pH6.0, with a sedimentation coefficient of 5.54S and mol.wt. 1.03×105, as determined by sedimentation-equilibrium measurements.

ACETYLASPARTIC ACID AND AMMONIA POISONING

1960 ◽  
Vol 38 (1) ◽  
pp. 763-768 ◽  
Author(s):  
Jean-Paul Du Ruisseau
Keyword(s):  
Amino Acid ◽  
Ammonium Acetate ◽  
Normal Liver ◽  
The Other ◽  
Normal Brain ◽  
High Concentrations ◽  
The One ◽  
Ammonia Poisoning

Acetylaspartic acid has been followed in nine tissues of normal and ammonia-poisoned rats. This acetylated amino acid is present at high concentrations in normal brain and remains unchanged in ammonia-poisoned brain. Acetylaspartic acid is absent or present in trace amounts in normal liver. It increases appreciably in ammonium acetate poisoning, reaching a peak at death. No change in concentration was detectable in the other tissues examined. There is a correlation between aspartic and acetylaspartic acid in the liver. But no correlation was observed between acetylaspartic acid on the one hand and ammonia and urea on the other. The possible origins of acetylaspartic acid are discussed.

Distribution and postprandial release of porcine peptide YY

1987 ◽  
Vol 113 (1) ◽  
pp. 11-14 ◽  
Author(s):  
T. E. Adrian ◽  
A. J. Bacarese-Hamilton ◽  
H. A. Smith ◽  
P. Chohan ◽  
K. J. Manolas ◽  
...  
Keyword(s):  
Amino Acid ◽  
Peptide Yy ◽  
Species Difference ◽  
Gel Permeation Chromatography ◽  
Molecular Forms ◽  
Distal Small Intestine ◽  
Identical Position ◽  
High Concentrations ◽  
Hormonal Peptide ◽  
Very High

ABSTRACT Peptide YY (PYY), a thirty-six amino acid intestinal hormonal peptide with a tyrosine residue at each end (hence YY as Y represents tyrosine in the new peptide nomenclature), was found throughout the gastrointestinal tract of the pig. Concentrations were very low in the foregut (antrum, 3·4 ± 0·3 pmol/g; duodenum, 1·1 ± 1·5 pmol/g), higher in the distal small intestine (ileum, 100 ± 13 pmol/g) and very high in the large bowel (descending colon, 270 ± 45 pmol/g). Peptide YY was found to circulate in plasma and concentrations rose substantially in response to eating (fasting, 138 ± 15 pmol/l; postprandial, 263 ± 21 pmol/l; P<0·001). There was a small but significant portal/arterial gradient in postprandial PYY levels. More than 90% of the immunoreactive PYY in gut extracts eluted, on gel permeation chromatography, in an identical position to pure PYY standard, but small amounts of higher molecular weight material, possibly precursors, were detected. In contrast, plasma from fasting pigs contained a large proportion (60–70%) of these large molecular forms. These findings suggest that the putative pro-PYY may be cleared more slowly from the circulation than the 36 amino acid hormonal peptide. The high concentrations of immunoreactive PYY in the circulation of the young pig may reflect a species difference between pig and man or may indicate an important role for PYY in the developing animal. J. Endocr. (1987) 113, 11–14

The Retention of Amino Acids in the Haemolymph During Diuresis in Rhodnius

1980 ◽  
Vol 87 (1) ◽  
pp. 315-330
Author(s):  
S.H.P. MADDRELL ◽  
B.O.C. GARDINER
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
High Rate ◽  
Excretory System ◽  
Low Permeability ◽  
High Concentrations ◽  
Active Reabsorption ◽  
Very High

The haemolymph of Rhodnius is rich in amino acids. During the rapid diuresis after a blood meal, no more than trace amounts of amino acids are lost in the urine. There is no significant reabsorption of amino acids in the excretory system. That they escape elimination can instead be attributed to a combination of the low permeability of the Malpighian tubules to amino acids, the very high rate of fluid secretion by the tubules, and the dilution of the haemolymph by an expansion in its volume after feeding. Amino acid losses are low in spite of the fact that the tubules actively accumulate high concentrations of amino acids in their cells and passive losses from these stores augment to some extent the flux of amino acids into the lumen. At times other than during diuresis, fluid secretion by the Malpighian tubules is slow. Calculations show that haemolymph solutes can then passively reach the higher concentrations in the lumen that are required for the operation of the excretory system (which relies on unselective passive entry and active reabsorption of useful substances). An advantage of the extraordinarily high rate of fluid secretion during diuresis is that fluid excretion can be rapidly completed. There is then little time for significant amounts of haemolymph solute to be lost passively.

The Kinetics and Mechanism of a Reaction in Which Ligand Substitution is Accompanied by a Spin-State Change: Observation of the Elusive Monodithiocarbamatonickel(II) Complex in Dimethyl Sulfoxide

1979 ◽  
Vol 32 (8) ◽  
pp. 1679 ◽  
Author(s):  
PJ Nichols ◽  
MW Grant
Keyword(s):  
Dimethyl Sulfoxide ◽  
Electronic Spectrum ◽  
Ligand Substitution ◽  
The Other ◽  
Direct Reaction ◽  
State Change ◽  
Low Concentrations ◽  
High Concentrations ◽  
Dimerization Reaction ◽  
Very High

In solutions in Me2SO containing low concentrations of diethyldithiocarbamate ion (dtc-) and very high concentrations of Ni(Me2SO)62+ ion, the hitherto undetected Ni(dtc)+ complex is kinetically stabilized and its electronic spectrum can be recorded. The mono complex is thermodynamically unstable and is converted into Ni(dtc)2 by two independent pathways, one involving direct reaction between Ni(dtc)+ and dtc-, the other being a dimerization reaction, 2Ni(dtc)+ → Ni2+ + Ni(dtc)2. Analysis of the mechanistic scheme Ni2+ + dtc ↔ Ni(dtc)2 Ni(dtc)+ + dtc- → Ni(dtc)2 2Ni(dtc)+ → Ni2+ + Ni(dtc)2 gives k1 = 3 × 103 l, mol-1 s-1, k-1 ≈ 0.01 s-1, k2 ≈ 4 × 105 l, mol-1 s-1 and k3 ≈ 1 × 103 l. mol-1 s-1. Coordinated dtc- exerts a significant labilizing effect on coordinated Me2SO molecules in Ni(dtc)+.

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