Effects of amino acids on Thiobacillus acidophilus. II. Threonine deaminase

1980 ◽  
Vol 26 (3) ◽  
pp. 385-388 ◽  
Author(s):  
Gérald Proteau ◽  
Marvin Silver
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Ammonium Sulfate ◽  
Active Site ◽  
Binding Sites ◽  
Threonine Deaminase ◽  
Low Concentrations ◽  
High Concentrations ◽  
Thiobacillus Acidophilus ◽  
Optimal Ph

Biosynthetic L-threonine deaminase was partially purified 73-fold with a 60% recovery from Thiobacillus acidophilus by ammonium sulfate fractionation and by Sepharose 6B-C1 chromatography. The optimal pH for enzyme activity was between 9.0 and 10.0 and no optimal pH shift was observed in the presence of L-isoleucine, an inhibitor. The enzyme was effectively inhibited by L-isoleucine and showed homotropic interaction only in the presence of L-isoleucine.Kinetic studies indicate that there are at least two threonine binding sites and at least two isoleucine binding sites. The Km for threonine is 2.5 × 10−3 M. The inhibition due to isoleucine is reversed by low concentrations of L-valine. L-Valine at high concentrations acts as a substrate analogue and competitively inhibits L-threonine binding at the active site; the K1 is 1.6 × 10−2 M.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

Furosemide-sensitive thallium fluxes in smooth muscle of rabbit uterus

1983 ◽  
Vol 245 (6) ◽  
pp. F778-F783
Author(s):  
A. Johns ◽  
S. V. Cutshaw
Keyword(s):  
Smooth Muscle ◽  
Binding Sites ◽  
Rank Order ◽  
Chloride Concentration ◽  
Cation Binding ◽  
Exchange System ◽  
Total Uptake ◽  
Low Concentrations ◽  
Chloride Pump ◽  
High Concentrations

The furosemide-sensitive uptake of thallium represents approximately equal to 50% of the total uptake of thallium by rabbit uterus and requires Cl- and Na+. The furosemide-sensitive uptake of thallium is stimulated by other ions at low concentrations with the rank order Li+ greater than Tl+ greater than K+ = Rb+ greater than Cs+ and is inhibited by these ions at high concentrations with the rank order Tl+ greater than K+ = Rb+ greater than Cs+ greater than Li+, suggesting multiple cation binding sites on the carrier. Uptake of 36Cl- is inhibited by furosemide in the presence of ouabain. Thallium efflux and 36Cl efflux in the presence of ouabain is inhibited by furosemide. The chloride concentration regulates the proportion of thallium uptake that is ouabain sensitive and furosemide sensitive without altering the total uptake. It is suggested that the furosemide-sensitive uptake of thallium reflects a Na+-Cl- -K+ exchange system that could be classified as a cotransport or countertransport of any two of these ions and also could be the smooth muscle chloride pump.

scholarly journals The Relation of the Composition of the Culture Medium to the Formation of Endospores by Aerobic Bacilli

1932 ◽  
Vol 32 (4) ◽  
pp. 535-543 ◽  
Author(s):  
H. L. A. Tarr
Keyword(s):  
Amino Acids ◽  
Culture Medium ◽  
Inorganic Salt ◽  
Synthetic Medium ◽  
Ammonium Phosphate ◽  
Spore Formation ◽  
Experimental Conditions ◽  
Nitrogenous Compounds ◽  
Low Concentrations ◽  
High Concentrations

1. Spore formation in eight typical members of the genusBacillushas been studied.2. Three of these strains, including one species ofB. anthracis, have been found to be practically asporogenous under the experimental conditions. In general the following statements hold good for the sporogenous races studied.3. Spore formation is almost, or entirely, inhibited by cultivation on media rich in amino acids, such as tryptic digests of casein or meat. Similar inhibition results following cultivation on a medium containing reasonably high concentrations of a mixture of amino acids and asparagine.4. When such media are suitably diluted with standard inorganic salt solutions the percentage of spores formed is greatly increased, and frequently at least 99 per cent. of spores are formed if the dilution is sufficiently high.5. When simple nitrogenous compounds such as amino acids are added to a dilute casein digest medium in which sporulation is almost complete, a definite decrease in the percentage of spores present is observed. Asparagine, which is probably readily assimilated, apparently completely hinders spore formation in most cases. Other amino acids do not exert so pronounced an effect, and ammonium phosphate does not appreciably inhibit the formation of spores.6. The fact that the addition of glycine suppresses growth markedly when it is added to a dilute casein digest medium, but does not appreciably hinder sporulation, suggests that the formation of spores is not due to any toxic effect of added compounds, or compounds already present in the medium.7. Sporulation is almost complete in a “synthetic” medium in which low concentrations of ammonium phosphate and sucrose represent the sources of nitrogen and carbon, respectively. However, frequent transfers in such a medium may inhibit spore formation partially or entirely in certain instances. This effect probably depends upon the enhanced ability of the culture in question to utilise sucrose as a source of carbon when cultivated constantly in its presence.8. It is concluded, from the above data, that endospore formation in aerobic bacilli bears an inverse relationship to the amount of available nutrient material present in the culture medium.I am indebted to Prof. Sir F. G. Hopkins and Miss M. Stephenson for their constant encouragement during the progress of this work. My thanks are due to Mr Pirie of this Department who kindly furnished me with several of the amino acids employed, and to Dr Miles of the Department of Pathology for his kindness in supplying me with certain of the cultures.

scholarly journals Temperature and the regulation of enzyme activity in poikilotherms. Properties of rainbow-trout fructose diphosphatase

1969 ◽  
Vol 111 (3) ◽  
pp. 287-295 ◽  
Author(s):  
H. W. Behrisch ◽  
P. W. Hochachka
Keyword(s):  
Enzyme Activity ◽  
Rainbow Trout ◽  
Temperature Adaptation ◽  
Temperature Dependent ◽  
Ph Optimum ◽  
Physiological Temperature ◽  
Low Concentrations ◽  
High Concentrations ◽  
Regulation Of Enzyme Activity ◽  
Hill Plots

1. The properties of fructose diphosphatase from the liver of rainbow trout (Salmo gairdnerii) were examined over the physiological temperature range of the organism. 2. Saturation curves for substrate (fructose 1,6-diphosphate) and a cofactor (Mg2+) are sigmoidal, and Hill plots of the results suggest a minimum of two interacting fructose 1,6-diphosphate sites and two interacting Mg2+ sites per molecule of enzyme. 3. Mn2+-saturation curves are hyperbolic, and the Ka for Mn2+, which inhibits the enzyme at high concentrations, is 50–100-fold lower than the Ka for Mg2+. 4. Fructose diphosphatase is inhibited by low concentrations of AMP; this inhibition appears to be decreased and reversed by increasing the concentrations of Mg2+ and Mn2+. Higher concentrations of AMP are required to inhibit the trout fructose diphosphatase in the presence of Mn2+. 5. The affinities of fructose diphosphatase for fructose diphosphate and Mn2+ appear to be temperature-independent, whereas the affinities for Mg2+ and AMP are highly temperature-dependent. 6. The pH optimum of the enzyme depends on the concentrations of Mg2+ and Mn2+. In addition, pH determines the Ka for Mg2+; at high pH, Ka for Mg2+ is lowered. 7. The enzyme is inhibited by Ca2+ and Zn2+, and the inhibition is competitive with respect to both cations. 8. The possible roles of these ions and AMP in the modulation of fructose diphosphatase and gluconeogenic activity are discussed in relation to temperature adaptation.

ESSENTIAL AMINO ACIDS IN MICROORGANISMS

1957 ◽  
Vol 3 (5) ◽  
pp. 721-728 ◽  
Author(s):  
F. Reusser ◽  
J. F. T. Spencer ◽  
H. R. Sallans
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Quantitative Method ◽  
Essential Amino Acids ◽  
Cellular Protein ◽  
One Dimensional ◽  
Low Concentrations ◽  
Amino Acid Determination ◽  
High Concentrations ◽  
Acid Determination

The cells of 19 species of bacteria, actinomyces, and yeasts were analyzed for protein and essential amino acids. A rapid quantitative method for amino acid determination using one-dimensional paper chromatography was developed. The cellular protein from all species contained relatively high concentrations of lysine, somewhat lower concentrations of tryptophan and threonine, and very low concentrations of methionine. All of the 10 essential amino acids were found in each species tested, although individual differences in the relative and absolute amounts were observed.

scholarly journals Calcitonin Gene-Related Peptide (Cgrp), Adrenomedullin (Am), Amylin, And Calcitonin (Ct) Receptors And Overlapping Biological Actions

2001 ◽  
Vol 1 ◽  
pp. 4-4 ◽  
Author(s):  
J.A. Fischer ◽  
W. Born ◽  
R. Muff
Keyword(s):  
Receptor Binding ◽  
Binding Sites ◽  
Glycogen Synthesis ◽  
Orphan Receptor ◽  
Cgrp Receptor ◽  
Low Concentrations ◽  
Ring Structures ◽  
High Concentrations ◽  
Receptor Activity Modifying Proteins ◽  
Biological Actions

CGRP, AM, amylin, and CT have in common N-terminal 6-7 amino acid ring structures linked by disulfide bridges and amidated C-termini required for biological activity. For the related bioactive peptides, receptor-binding sites linked to cAMP stimulation and to a lesser extent to the phospholipase C signaling pathway have been identified in tissue specific manner. The highest density of CGRP receptors has been recognized in the cerebellum and the spinal cord. There photoaffinity-labeled N-glycosylated 60,000 and 54,000 Mr proteins are converted to 46,000 and 41,000 Mr components following endoglycosidase F/N-glycosidase F treatment. The same proteins were specifically labeled with [125I]-hCGRP-I(1-37) and -(8-37). Some cross-reaction between the CGRP receptor and AM was evident whereas amylin and CT were only recognized at over 10-7 M. A different AM receptor localized predominantly in the lung recognized CGRP at low, and amylin and calcitonin at equally high concentrations. CT receptor binding sites have been identified in osteoclasts and in the periventricular region of the brain. They cross-reacted with amylin at low concentrations and with CGRP and AM at over 10-7 M. Amylin receptor binding sites cross-reacting with salmon CT and CGRP but not with hCT and adrenomedullin to any great extent were originally described by Sexton in the nucleus accumbens and may represent a second CGRP receptor. The structure of a CT receptor was elucidated by the group of Goldring in 1991 through molecular cloning, and of a 60% homologous human CT receptor-like receptor (CRLR) shortly thereafter here. The latter was an orphan receptor until the discovery of the receptor-activity-modifying proteins (RAMP) by Foord which upon coexpression yield a CGRP receptor with RAMP1 and an AM receptor with RAMP2. Coexpression of the hCT receptor isotype 2 revealed a CGRP/amylin receptor with RAMP1 and an amylin receptor isotype with RAMP3. The CRLR/RAMP1 receptor antagonized by CGRP(8-37) corresponds to the CGRP1 receptor defined by Quirion, whereas his CGRP2 receptor remains to be identified. Another CGRP receptor isotype remains to be discovered in the cerebellum with no detectable CRLR encoding mRNA. Overlapping biological actions include inhibition of bone resorption obtained predominantly with CT, but also at high concentrations with CGRP, AM, and amylin. CGRP and AM are potent vasodilators, an effect shared with CT at pharmacological concentrations. Biological actions of amylin include suppression of insulin secretion, stimulation of glycogenolysis and inhibition of glycogen synthesis. In conclusion, the hCT2 receptor or the CRLR are associated with one of three RAMPs to bind to CGRP, AM, or amylin.

scholarly journals Mode of Action of the Bordetella BvgA Protein: Transcriptional Activation and Repression of the Bordetella bronchiseptica bipA Promoter

2005 ◽  
Vol 187 (18) ◽  
pp. 6290-6299 ◽  
Author(s):  
Meenu Mishra ◽  
Rajendar Deora
Keyword(s):  
Transcriptional Activation ◽  
Binding Sites ◽  
Expression Profiles ◽  
Regulation Of Gene Expression ◽  
Binding Assays ◽  
Specific Expression ◽  
Low Concentrations ◽  
Complex Regulation ◽  
High Concentrations

ABSTRACT The Bordetella BvgAS signal transduction system controls the transition among at least three known phenotypic phases (Bvg+, Bvgi, and Bvg−) and the expression of a number of genes which have distinct phase-specific expression profiles. This complex regulation of gene expression along the Bvg signaling continuum is best exemplified by the gene bipA, which is expressed at a low level in the Bvg+ phase, at a maximal level in the Bvgi phase, and at undetectable levels in the Bvg− phase. The bipA promoter has multiple BvgA binding sites which play distinct regulatory roles. We had previously speculated that the expression profile of bipA is a consequence of the differential occupancy of the various BvgA binding sites as a result of variation in the levels of phosphorylated BvgA (BvgA-P) inside the cell. In this report, we provide in vitro evidence for this model and show that bipA expression is activated at low concentrations of BvgA-P and is repressed at high concentrations. By using independent DNA binding assays, we demonstrate that under activating conditions there is a synergistic effect on the binding of BvgA and RNA polymerase (RNAP), leading to the formation of open complexes at the promoter. We further show that, under in vitro conditions, when bipA transcription is minimal, there is competition between the binding of RNAP and BvgA-P to the bipA promoter. Our results show that the BvgA binding site IR2 plays a central role in mediating this repression.

scholarly journals Influx of calcium, strontium, and barium in presynaptic nerve endings.

1982 ◽  
Vol 79 (6) ◽  
pp. 1065-1087 ◽  
Author(s):  
D A Nachshen ◽  
M P Blaustein
Keyword(s):  
Divalent Cation ◽  
Binding Sites ◽  
Divalent Cations ◽  
Ion Selectivity ◽  
Permeability Ratio ◽  
Low Concentrations ◽  
Slow Channel ◽  
Channel Selectivity ◽  
High Concentrations ◽  
Two Phases

Depolarization-induced (potassium-stimulated) influx of 45Ca, 85Sr, and 133Ba was measured in synaptosomes prepared from rat brain. There are two phases of divalent cation entry, "fast" and "slow;" each phase is mediated by channels with distinctive characteristics. The fast channels inactivate (within 1 s) and are blocked by low concentrations (less than 1 micro M) of La. The slow channels do not inactivate (within 10 s), and are blocked by high concentrations (greater than 50 micro M) of La. Divalent cation influx through both channels saturates with increasing concentrations of permeant divalent cation; in addition, each permeant divalent cation species competitively blocks the influx of other permeant species. These results are consistent with the presence of "binding sites" for divalent cations in the fast and slow channels. The Ca:Sr:Ba permeability ratio, determined by measuring the influx of all three species in triple-label experiments, was 6:3:2 for the fast channel and 6:3:1 for the slow channel. A simple model for ion selectivity, based on the presence of a binding site in the channel, could account well for slow and, to some extent, for fast, channel selectivity data.

scholarly journals Carbohydrate content of insoluble elastins prepared from adult bovine and calf ligamentum nuchae and tropoelastin isolated from copper-deficient procine aorta

1971 ◽  
Vol 121 (2) ◽  
pp. 197-202 ◽  
Author(s):  
M. E. Grant ◽  
F. S. Steven ◽  
D. S. Jackson ◽  
L. B. Sandberg
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Carbohydrate Content ◽  
Amino Sugars ◽  
Collagenase Digestion ◽  
Low Concentrations ◽  
Neutral Sugars ◽  
High Concentrations ◽  
Edta Extraction

1. Insoluble elastin has been prepared by several different methods from adult bovine and calf ligamentum nuchae. Highly purified tropoelastin has been prepared from copper-deficient porcine aorta. 2. Amino acid analyses indicated that all preparations, except that obtained from calf ligamentum nuchae by using an EDTA extraction followed by collagenase digestion (preparation E6), were typical of pure elastin having high concentrations of hydrophobic and low concentrations of hydrophilic amino acids. Preparation E6 was found to contain approx. 40% collagen. 3. The determination and composition of the carbohydrates associated with these preparations is reported. With the exception of preparation E6, the insoluble elastins contained only trace amounts of neutral sugars (0.13–0.35%, w/w) and amino sugars (0.01–0.06%, w/w). The porcine tropoelastin contained virtually no carbohydrate. 4. The results suggest that carbohydrate analyses can yield valuable information about the purity of elastin preparations.

scholarly journals An Exported Inducer Peptide Regulates Bacteriocin Production in Enterococcus faecium CTC492

1998 ◽  
Vol 180 (7) ◽  
pp. 1848-1854 ◽  
Author(s):  
Trine Nilsen ◽  
Ingolf F. Nes ◽  
Helge Holo
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Enterococcus Faecium ◽  
Low Ph ◽  
Bacteriocin Production ◽  
Leader Peptide ◽  
Amino Acid Sequencing ◽  
High Concentrations ◽  
Enterocin A ◽  
Optimal Ph

ABSTRACT Production of the bacteriocins enterocin A and enterocin B inEnterococcus faecium CTC492 was dependent on the presence of an extracellular peptide produced by the strain itself. This induction factor (EntF) was purified, and amino acid sequencing combined with DNA sequencing of the corresponding gene identified it as a peptide of 25 amino acids. The gene encodes a prepeptide of 41 amino acids, including a 16-amino-acid leader peptide of the double-glycine type. Environmental factors influenced the level of bacteriocin production in E. faecium CTC492. The optimal pH for bacteriocin production was 6.2. At pH 5.5, growth was slow, and very little bacteriocin was formed. The presence of NaCl or ethanol (EtOH) was also inhibitory to bacteriocin production, and at high concentrations of these solutes, no bacteriocin production was observed. The induction factor induced its own synthesis, and by dilution of the culture 106 times or more, nonproducing cultures were obtained. Bacteriocin production was induced in these cultures by addition of EntF. The response was linear, and low bacteriocin production could be induced by about 10−17 M EntF. This response was attenuated by low pH or the presence of high concentrations of NaCl or EtOH, and 300 times more EntF was needed to induce detectable bacteriocin production in the presence of 6.5% NaCl. High levels of bacteriocin production in cultures grown at low pH or in the presence of high concentrations of NaCl or EtOH were obtained by addition of sufficient amounts of EntF.

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