Research Interests: Brazil, Mice, Female, Animals, Male, and 8 moreLectins, Proteins, Plant Lectins, Amino Acids, Molecular weight, Amino Acid Sequence, PLANT PROTEINS, and Toxicon
Crude venom from Bothrops jararaca has procoagulant, platelet aggregating and phospholipase A2 (PLA2) activities. By chromatographic fractionation of the venom on Sephacryl S-200 it was possible to separate these three activities and to... more
Crude venom from Bothrops jararaca has procoagulant, platelet aggregating and phospholipase A2 (PLA2) activities. By chromatographic fractionation of the venom on Sephacryl S-200 it was possible to separate these three activities and to show that distinct protein components are involved. The procoagulant activity appears to involve the synergistic action of several components and was not further studied in the present work. The aggregating activity results from the action of two components: 1) a serino-proteinase PMSF-inhibitable similar to thrombocytin and 2) a PMSF-resistant, calcium- and plasma-dependent factor distinct from other previously described aggregating principles. Fractions possessing PLA2 activity were also able to inhibit platelet aggregation induced by collagen and accelerated the slow reversal of aggregation induced by ADP. Both PLA2 activity and inhibition of collagen-induced platelet aggregation displayed by these fractions were abolished by reaction with p-bromophenacyl bromide and 2-mercapto-ethanol. These results indicate that in B. jararaca venom the PLA2 activity and the factor inhibiting platelet aggregation may be related to the same protein molecule.
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Canatoxin (CNTX), the toxic protein from Canavalia ensiformis seeds, injected into the peritoneal cavities of mice (10 micrograms/cavity) induced a significant neutrophil migration (10.5 +/- 0.5 x 10(6) cells/cavity) after 4 h. A later... more
Canatoxin (CNTX), the toxic protein from Canavalia ensiformis seeds, injected into the peritoneal cavities of mice (10 micrograms/cavity) induced a significant neutrophil migration (10.5 +/- 0.5 x 10(6) cells/cavity) after 4 h. A later migratory effect (48 h) on mononuclear cells, predominantly macrophages, was also observed (controls: 7 +/- 0.9; CNTX: 17 +/- 2.0 x 10(6) cells/cavity). These CNTX-elicited macrophages, when compared to resident cells (R) or cells elicited by thioglycollate (TG), had an increased content of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (R: 4.5 +/- 0.5; TG: 7.2 +/- 1.0; CNTX: 20.2 +/- 3.0 mU/10(6) cells) and a greater (> or = 100%) phagocytic activity. The data suggest that CNTX-stimulated macrophages presented some characteristics of activated cells.
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Six venoms from snakes of the genus Bothrops were tested for coagulation, platelet aggregation and phospholipase A2 (PLA2) activity. Almost all showed pro-coagulant and PLA2 activities while pro-aggregating properties were found only for... more
Six venoms from snakes of the genus Bothrops were tested for coagulation, platelet aggregation and phospholipase A2 (PLA2) activity. Almost all showed pro-coagulant and PLA2 activities while pro-aggregating properties were found only for some venoms. Bothrops jararaca venom showed different protein peaks associated with these activities. The pro-aggregating activity was inhibited by EDTA, leupeptin and mepacrine while the PLA2 activity was blocked by p-bromophenacyl bromide and 2-mercaptoethanol. Venom screening tests for clotting and platelet aggregation may represent a valuable tool for snake taxonomy and for monitoring the quality of antisera.
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Canatoxin, a convulsant neurotoxin from the seeds of Canavalia ensiformis, induces lipoxygenase-dependent hypoxia and sex-related alterations of carbohydrate metabolism in rats which are blocked by glucose, diazepam and hexamethonium. The... more
Canatoxin, a convulsant neurotoxin from the seeds of Canavalia ensiformis, induces lipoxygenase-dependent hypoxia and sex-related alterations of carbohydrate metabolism in rats which are blocked by glucose, diazepam and hexamethonium. The present study analyzes the possible casual relationship between the convulsant action of canatoxin and its effects on carbohydrate metabolism. The incidence of canatoxin-induced convulsions was greater in male than in female rats. Pretreatment of male rats with drugs that block hypoxia, such as glucose (2.5 g/kg, iv, 15 min), diazepam (5 mg/kg, ip, at 48 h, 24 h and 15 min), hexamethonium (4 mg/kg, ip, 15 min) and NDGA (125 mg/kg, ip, 1 h), also protected the animals against convulsions, respiratory distress and death. These results suggest that canatoxin-induced convulsions are probably the consequence of hypoxia and both effects are mediated by lipoxygenase activation.
Research Interests: Anoxia, Blood Glucose, Liver, Female, Animals, and 7 moreMale, Lectins, Rats, Seizures, Lethal Dose, PLANT PROTEINS, and Aspartate Aminotransferases
1. The effects of canatoxin, the toxic principle from Canavalia ensiformis seeds which has lipoxygenase-activating properties, were evaluated in rats using radioimmunoassay techniques to measure plasma levels of prolactin (PRL),... more
1. The effects of canatoxin, the toxic principle from Canavalia ensiformis seeds which has lipoxygenase-activating properties, were evaluated in rats using radioimmunoassay techniques to measure plasma levels of prolactin (PRL), progesterone, follicle stimulating (FSH) and luteinizing (LH) hormones. 2. The chronic administration of canatoxin (50, 100 or 200 micrograms/kg daily for 12 days, ip) to female rats induced a sharp rise in plasma LH and FSH concentrations with no changes in progesterone level. A fall in circulating PRL was also observed. The frequency of proestrus and weight gain increased in rats treated with the highest dose of toxin used, but there was no alteration in weight of uterus or ovaries. 3. The increases in gonadotropin levels with canatoxin are consistent with the lipoxygenase-activating properties of the toxin, but do not explain why plasma PRL concentrations decreased in canatoxin-treated rats. 4. Since the animals in the control group had high PRL and low LH levels and since canatoxin increased LH and decreased PRL in the circulation, a possible stress-prevention effect is discussed for the toxin. 5. This study supports previous suggestions of central actions for canatoxin, and indicates the hypophysis and/or hypothalamus as one of the target sites for the toxin in the central nervous system.
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Canatoxin (CNTX), a neurotoxic protein, is known to activate platelet secretion and aggregation in vitro through a lipoxygenase-dependent pathway. This study shows that CNTX also induces time and dose-dependent serotonin secretion from... more
Canatoxin (CNTX), a neurotoxic protein, is known to activate platelet secretion and aggregation in vitro through a lipoxygenase-dependent pathway. This study shows that CNTX also induces time and dose-dependent serotonin secretion from rat brain synaptosomes. The secretory effect induced by 6 microM CNTX was similar to that elicited by 150 mM KCl. Nordihydroguaiaretic acid (500 microM) completely abolished CNTX-induced serotonin release while 150 microM indomethacin had no effect. These data suggest the involvement of the lipoxygenase pathway in neurotransmitter release elicited by CNTX as occurs in the platelet.
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In the present report we show that convulxin (Cvx), a C-type lectin from Crotalus durissus terrificus venom, induces platelet agregation and phospholipase C (PLC) activation by a protein tyrosine kinase (PTK)-dependent pathway. In... more
In the present report we show that convulxin (Cvx), a C-type lectin from Crotalus durissus terrificus venom, induces platelet agregation and phospholipase C (PLC) activation by a protein tyrosine kinase (PTK)-dependent pathway. In addition, Cvx stimulates a rapid increase in tyrosine phosphorylation of human platelet proteins with molecular masses of 40, 72/74, 78/80 and 120 kDa, followed by dephosphorylation of some proteins. However, platelet aggregation was accompanied by the phosphorylation of a 105-kDa molecular mass protein. Furthermore, Cvx stimulates a rapid-tyrosyl phosphorylation of a 145-kDa protein that was identified as PLC gamma 2. Protein tyrose phosphatase (PTP) induced by Cvx was not blocked when platelets were stimulated in the presence of indomethacin, apyrase, EDTA or RGDS peptide, but inhibited by staurosporine and genistein. These results indicate that PTP is chronologically proximal to Cvx binding to platelets, and it is independent of platelet aggregation or fibrinogen binding to integrin alphaIIbbeta3. On the other hand, the phosphorylation step, and the phosphorylation of the 105-kDa protein, were both inhibited by RGDS and EDTA, which suggests that the integrin alphaIIbbeta3 beta is involved in these steps. Our results, taken together, show that Cvx induces platelet IIb 3 aggregation in a similar manner as collagen and collagen-related peptides that also trigger platelet aggregation by a PTK-dependent pathway, and stimulate tyrosyl-phosphorylation of PLC gamma 2. However, Cvx is unique among platelet receptor agonists, because under test-tube stirring conditions it induces a PTP profile independently of integrin alphaIIbbeta3.
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A lectin was purified from seeds of Erythrina velutina forma aurantiaca by affinity chromatography on cross-linked guar gum. The lectin is a potent agglutinin for human (minimal concentration of protein able to cause visible agglutination... more
A lectin was purified from seeds of Erythrina velutina forma aurantiaca by affinity chromatography on cross-linked guar gum. The lectin is a potent agglutinin for human (minimal concentration of protein able to cause visible agglutination of a 2% erythrocyte suspension varying from 1 to 4 micrograms/ml), rabbit (4 micrograms/ml) and chicken erythrocytes (8 micrograms/ml) but presented low activity against cow (250 micrograms/ml) or sheep (333 micrograms/ml) blood cells. Hemagglutination of human O+ erythrocytes was inhibited by D-lactose (0.2 mM) > D-galactose (0.8 mM) > D-raffinose (2.1 mM). At pH 7.5, chromatography on a Superose 12 HR 10/30 column showed that the lectin was primarily a dimer (56.0 kDa) composed of two identical subunits (31.6 kDa each). A small amount of a tetrameric form was also apparently present. The lectin is a glycoprotein (7.3% carbohydrate), has a pI of 4.5, contains high levels of acidic (Asp and Glu, 64.2 and 51.6 residues/mol, respectively) and hydroxy amino acids (Ser and Thr, 42.9 and 38.5 residues/mol, respectively) but relatively low amounts of sulfur amino acids (Cys and Met, 1.0 and 5.0 residues/mol, respectively) and has an N-terminal sequence of Val-Glu-Thr-Ile/Leu-Pro-Phe-Ser. Its hemagglutinating activity was abolished by heating at 70 degrees C for 10 min. The activation energy (delta G') required for denaturation measured by loss of hemagglutination activity was 24.87 kcal/mol. In rats, the purified lectin (100 micrograms) induced neutrophil migration into the peritoneal cavity (3.7 +/- 0.6 x 10(6) neutrophils/ml) or into the air pouch (2.75 +/- 0.25 x 10(6) neutrophils/ml), 8 and 10 times greater than the negative control, respectively.
Research Interests: Brazil, Medicinal Plants, Humans, Animals, Lectins, and 5 morePlant Lectins, Rats, Seeds, Brazilian, and Wistar Rats
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Screening of the biochemical-pharmacological properties of the crude venom from the snake Lachesis muta indicated the presence of phospholipase A2 (PLA2; 5260 U/mg protein), procoagulant (2630 U/mg protein), platelet aggregating (43 U/mg... more
Screening of the biochemical-pharmacological properties of the crude venom from the snake Lachesis muta indicated the presence of phospholipase A2 (PLA2; 5260 U/mg protein), procoagulant (2630 U/mg protein), platelet aggregating (43 U/mg protein) and caseinolytic activities (6670 U/mg protein). These activities were separated by filtration of the crude venom on Sephacryl S-200. The material containing PLA2 activity was further fractioned by DEAE-cellulose ion exchange chromatography into four active fractions (F-I to F-IV, containing 1.7, 1.2, 0.3, and 0.05% of the crude venom protein, respectively) by stepwise elution with buffers of increasing ionic strength. All fractions presented a molecular weight of approximately 15,000 and isoelectric points in the range pH 4.6-6.0. In addition to their indirect hemolytic activity, the partially purified fractions inhibited platelet aggregation induced either by collagen or thrombin. p-Bromophenacyl bromide-treated fractions lost both phospholipase A2 activity and their inhibitory effect on collagen-induced platelet aggregation.
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1. Canatoxin, a protein displaying lipoxygenase-activating properties isolated from Canavalia ensiformis seeds, induces hypoxia and hyperglycemia in male rats. 2. Liver glycogen, blood glucose and lactate levels were measured in male and... more
1. Canatoxin, a protein displaying lipoxygenase-activating properties isolated from Canavalia ensiformis seeds, induces hypoxia and hyperglycemia in male rats. 2. Liver glycogen, blood glucose and lactate levels were measured in male and female rats after canatoxin (50 mU, iv) injection. Increased levels of serum glutamic oxaloacetic transaminase activity were used as an indicator of hepatic injury. 3. There was no sex-related difference observable during canatoxin-induced hypoxia but male and female rats did show different patterns of metabolic change and hepatic injury after toxin administration. Increased blood glucose and lactate levels, liver glycogenolysis and hepatic injury were observed in male rats while female rats showed only hypoglycemia and glycogenolysis. 4. Pretreatment of male rats with either glucose, diazepam or hexamethonium abolished both the hypoxia and hepatic injury and the metabolic alterations produced by toxin injection. 5. The results suggest that the meta...
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Until very recently, toxicity was not considered a trait observed in birds, but works published in the last two decades started to shed light on this subject. Poisonous birds are rare (or little studied), and comprise Pitohui and Ifrita... more
Until very recently, toxicity was not considered a trait observed in birds, but works published in the last two decades started to shed light on this subject. Poisonous birds are rare (or little studied), and comprise Pitohui and Ifrita birds from Papua New Guinea, the European quail, the Spoor-winged goose, the Hoopees, the North American Ruffed grouse, the Bronzewings, and the Red warbler. A hundred more species are considered unpalatable or malodorous to humans and other animals. The present review intends to present the current understanding of bird toxicity, possibly pointing to an ignored research field. Whenever possible, biochemical characteristics of these poisons and their effects on humans and other animals are discussed, along with historical aspects of poison discovery and evolutionary hypothesis regarding their function.
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Canatoxin is a toxic protein isolated from the jackbean, Canavalia ensiformis. The toxin injected intraperitoneally is lethal for mice and rats; however, it is inactive if given orally. In this study, Manduca sexta (L.) (Lepidoptera),... more
Canatoxin is a toxic protein isolated from the jackbean, Canavalia ensiformis. The toxin injected intraperitoneally is lethal for mice and rats; however, it is inactive if given orally. In this study, Manduca sexta (L.) (Lepidoptera), Schistocerca americana (Drury) (Orthoptera), Drosophila melanogaster (L.) (Diptera), Aedes aegypti (L.) (Diptera), Rhodnius prolixus (Stål) (Hemiptera), and Callosobruchus maculatus (F.) (Coleoptera) were fed on canatoxin-containing diets. No effects were seen in M. sexta, S. americana, D. melanogaster, or A. aegypti. No traces of canatoxin were found in their feces, suggesting that the protein was digested completely by these insects, which characteristically have a trypsin-based digestion. In contrast, canatoxin was lethal for insects displaying cathepsin-based digestion. Thus, for C. maculatus, a diet containing 0.25% wt:wt canatoxin caused complete inhibition of larval growth. When R. prolixus were fed on canatoxin, 2 effects were seen: impairment ...
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Some pharmacological-toxicological effects of canatoxin, a toxic protein purified from the seeds of Canavalia ensiformis have been studied in mice and rats. The most obvious effect, a lethal tonic convulsion, was generally produced 10-15... more
Some pharmacological-toxicological effects of canatoxin, a toxic protein purified from the seeds of Canavalia ensiformis have been studied in mice and rats. The most obvious effect, a lethal tonic convulsion, was generally produced 10-15 min. after intravenous injection of 2-3 mg/kg of the highly purified protein (mol. wt. 88,000). After intraperitoneal, intramuscular or subcutaneous administration the convulsion produced by the same toxin dosis occurred within 24 hours. A spinal transection at the midthoracic level did not abolish the convulsions of the hindlimbs while destruction of the medulla below this level completely blocked the convulsions of the hindlimbs. The convulsions of the head and forelimbs were unaffected by these surgical pretreatments. The toxic protein did neither affect the isolated skeletal muscle nor did it potentiate nerve impulse induced contractions. The convulsive effect of canatoxin was potentiated by reserpine and attenuated by phenobarbital, diazepam, m...
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Proteomics aimed at addressing sub cellular fractions, such as chloroplasts, are a complex challenge. In the past few years, several studies in different laboratories have identified and, more recently, quantified, thousands of proteins... more
Proteomics aimed at addressing sub cellular fractions, such as chloroplasts, are a complex challenge. In the past few years, several studies in different laboratories have identified and, more recently, quantified, thousands of proteins within whole chloroplasts or chloroplast fractions. A considerable number of these studies are available for querying, using online resources, such as databases containing the proteins identified, encoding genes, acquired spectra, and phosphopeptides. The main purpose of this review is to identity and highlight useful features of these online resourses, mainly focused in proteomics databases related to chloroplast research in Arabidopsis thaliana. Several web sites were consulted. Among them, 11 were selected and discussed herein. The databases were classified into Plastid Databases, General Organelle Proteome Databases, and General Arabidopsis Proteome Databases. Special care was taken to present information regarding protein identification, protein quantification, and data integration. A selected list of online resources is presented in two tables. The databases analyzed are a useful source of information for researchers in the plastid organelle and plant proteomics fields.
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Canatoxin, a toxic protein isolated from Canavalia ensiformis, was shown to inhibit DNA synthesis and to produce a cytolytic effect when added in vitro to various cells, in doses ranging from 50 to 500 nM. In this case no selectivity was... more
Canatoxin, a toxic protein isolated from Canavalia ensiformis, was shown to inhibit DNA synthesis and to produce a cytolytic effect when added in vitro to various cells, in doses ranging from 50 to 500 nM. In this case no selectivity was found for a certain cell type, as both normal and transformed cells could be affected by the toxic protein. The cytostatic effect was irreversible upon removal of the toxic protein from the medium and could be fully attained after exposing the cells to canatoxin for only 30 min. The use of an in vitro cell culture system may allow for a better insight on the mode of action of canatoxin.
Research Interests: Cell Biology, Cell Division, DNA, Spleen, Cell line, and 6 moreHumans, Animals, Cell Death, Lectins, PLANT PROTEINS, and Arachidonic Acid
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Research Interests: Insecticides, Animals, Insects, Toxins, Protein isoforms, and 3 moreCanavalia, PLANT PROTEINS, and Urease
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Research Interests: Mice, Animals, P-glycoprotein, Soybean, Glycoproteins, and 16 moreSodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis, High Performance Liquid Chromatography, Secondary Structure, Soybeans, Protein Secondary Structure Prediction, Spectrum analysis, Antifungal Agents, Molecular weight, Amino Acid Sequence, Glycine max, PLANT PROTEINS, Hemagglutination, Transgenic plant, Toxicon, Ammonium Sulfate, and Disulfide bond
ABSTRACT
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Intraplantar injection of canatoxin (CNTX) induced a dose-dependent rat hind-paw edema which was distinguished by two phases. In the first phase, observed between 0 and 2 hr after CNTX injection, there was an increase in paw volume, with... more
Intraplantar injection of canatoxin (CNTX) induced a dose-dependent rat hind-paw edema which was distinguished by two phases. In the first phase, observed between 0 and 2 hr after CNTX injection, there was an increase in paw volume, with no apparent involvement of inflammatory phagocytic cells. The second phase, beginning at about the 3rd hr, was characterized by an intense cellular infiltration at the site of administration which was coincident with a further increase in paw swelling. The edema was maximum at 6 hr after injection and disappeared within 48 hr at doses of 50-100 micrograms, while at doses of 200-300 micrograms edema was present in excess of 48 hr. The pharmacological studies suggested that CNTX-induced edema is a multi-mediated phenomenon. Histamine, serotonin, PAF and prostaglandins are likely involved in the first phase. Lipoxygenase metabolites, probably leukotrienes, seem to play a major role in the second phase, and may account for the development of cellular infiltration in the inflammatory site.
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Research Interests: Enzyme Inhibitors, Gene expression, Genetic Engineering, New Technology, Bacillus thuringiensis, and 14 moreInsect Resistance, Animals, Natural Product, Insects, Lectins, Enzyme, PLANT DEFENSE, Protease Inhibitors, Biopesticide, Mechanism of action, Amino Acid Sequence, PLANT PROTEINS, Transgenic plant, and Toxicon
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Canavalia ensiformis has three isoforms of urease: Jackbean urease (JBU), Jackbean urease II and canatoxin. These isoforms present several biological activities, independent from the enzymatic property, such as entomotoxicity and... more
Canavalia ensiformis has three isoforms of urease: Jackbean urease (JBU), Jackbean urease II and canatoxin. These isoforms present several biological activities, independent from the enzymatic property, such as entomotoxicity and antifungal properties. The entomotoxic activity is a property of the whole protein, as well as of a 10 kDa peptide released by insect digestive enzymes. Here we have used chemical modification to observe the influence of lysines and acidic residues on JBU enzymatic and insecticidal activities. Chemical modification of lysine residues was performed with dimethylamine-borane complex and formaldehyde, and acidic residues were modified by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and ethylenediamine. Derivatized ureases, called JBU-Lys (lysine-modified) and JBU-Ac (acidic residues-modified), were assayed for their biochemical and insecticidal properties. Neither modification altered significantly the kinetic parameters analyzed, indicating that no residue critical for the enzyme activity was affected and that the modifications did not incur in any significant structural alteration. On the other hand, both modifications reduced the toxic activity of the native protein fed to Dysdercus peruvianus. The changes observed in the entomotoxic property of the derivatized proteins reflect alterations in different steps of JBU's toxicity towards insects. JBU-Ac is not susceptible to hydrolysis by insect digestive enzymes, hence impairing the release of toxic peptide(s), while JBU-Lys is processed as the native protein. On the other hand, the antidiuretic effect of JBU on Rhodnius prolixus is altered in JBU-Lys, but not in JBU-Ac. Altogether, these data emphasize the role of lysine and acidic residues on the insecticidal properties of ureases.
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The distribution of three cross-reactive materials (CRMs), a toxic protein analogous to canatoxin, CNTX-CRM, a lectin analogous to concanavalin A, Con A-CRM, and a major storage protein, canavalin-CRM, was investigated during successive... more
The distribution of three cross-reactive materials (CRMs), a toxic protein analogous to canatoxin, CNTX-CRM, a lectin analogous to concanavalin A, Con A-CRM, and a major storage protein, canavalin-CRM, was investigated during successive stages of maturation of Canavalia brasiliensis Mart. seeds. The data obtained by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunological analyses indicated that these proteins share extensive homology with the analogous proteins found in Canavalia ensiformis seeds. The changes in CNTX-CRM and Con A-CRM levels throughout the maturation process were assayed by rocket immunoelectrophoresis. Synthesis of Con A-CRM was detectable at 30 days post-anthesis (DPA) while its hemagglutinating activity appeared only at 35 DPA. The CNTX-CRM was detected as a biologically active protein from 30 DPA onwards. The behavior of CNTX-CRM during maturation of C. brasiliensis seeds was quite distinct from that of Con A-CRM, pointing to different biological roles of these proteins in the seed.
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... A AMONG PROTEINS OF LEGUMINOUS SEEDS* CELIA R. CARLINI, GRACE 8. S, BARCELLOS,ARTHUR D. V, BAETA-NEVES and JORGE A, GUIMARAES Department of Biochemistry, InslItuto de Ciencias Biomedicas, Universidade Federal do Rio de JaneIro, cP... more
... A AMONG PROTEINS OF LEGUMINOUS SEEDS* CELIA R. CARLINI, GRACE 8. S, BARCELLOS,ARTHUR D. V, BAETA-NEVES and JORGE A, GUIMARAES Department of Biochemistry, InslItuto de Ciencias Biomedicas, Universidade Federal do Rio de JaneIro, cP 68041 ...
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The evolution in proteomics approaches is notable, including quantitative proteomics and strategies for elucidation of post-translational modifications. Faster and more accurate mass spectrometers as well as cleverer bioinformatics tolls... more
The evolution in proteomics approaches is notable, including quantitative proteomics and strategies for elucidation of post-translational modifications. Faster and more accurate mass spectrometers as well as cleverer bioinformatics tolls are making the difference in such advancement. Among the wide range of research in plant proteomics, biopharmaceutical production using plants as "biofactories" and the screening of new activities of new molecules, in this case, peptides, are quite important regarding translational proteomics. The present review is focused on "recombinant proteins and bioactive peptides", with biopharmaceuticals and cyclotides chosen as examples. Their application and challenges are focused on a "translational proteomics" point of view, in order to exemplify some new areas of research based on proteomics strategies. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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The bacterium Helicobacter pylori causes peptic ulcers and gastric cancer in human beings by mechanisms yet not fully understood. H. pylori produces urease which neutralizes the acidic medium permitting its survival in the stomach. We... more
The bacterium Helicobacter pylori causes peptic ulcers and gastric cancer in human beings by mechanisms yet not fully understood. H. pylori produces urease which neutralizes the acidic medium permitting its survival in the stomach. We have previously shown that ureases from jackbean, soybean or Bacillus pasteurii induce blood platelet aggregation independently of their enzyme activity by a pathway requiring platelet secretion, activation of calcium channels and lipoxygenase-derived eicosanoids. We investigated whether H. pylori urease displays platelet-activating properties and defined biochemical pathways involved in this phenomenon. For that the effects of purified recombinant H. pylori urease (HPU) added to rabbit platelets were assessed turbidimetrically. ATP secretion and production of lipoxygenase metabolites by activated platelets were measured. Fluorescein-labelled HPU bound to platelets but not to erythrocytes. HPU induced aggregation of rabbit platelets (ED(50) 0.28 microM) accompanied by ATP secretion. No correlation was found between platelet activation and ureolytic activity of HPU. Platelet aggregation was blocked by esculetin (12-lipoxygenase inhibitor) and enhanced approximately 3-fold by indomethacin (cyclooxygenase inhibitor). A metabolite of 12-lipoxygenase was produced by platelets exposed to HPU. Platelet responses to HPU did not involve platelet-activating factor, but required activation of verapamil-inhibitable calcium channels. Our data show that purified H. pylori urease activates blood platelets at submicromolar concentrations. This property seems to be common to ureases regardless of their source (plant or bacteria) or quaternary structure (single, di- or tri-chain proteins). These properties of HPU could play an important role in pathogenesis of gastrointestinal and associated cardiovascular diseases caused by H. pylori.
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... 4377. DOI: 10.1021/jf970466+. Publication Date (Web): November 17, 1997. Copyright © 1997 American Chemical Society. ... Bressani, R.; Brenes, RG; Garcia, A.; Elias, LG Chemical composition, aminoacid ... Ph.D. Thesis, Federal... more
... 4377. DOI: 10.1021/jf970466+. Publication Date (Web): November 17, 1997. Copyright © 1997 American Chemical Society. ... Bressani, R.; Brenes, RG; Garcia, A.; Elias, LG Chemical composition, aminoacid ... Ph.D. Thesis, Federal University of Technology, Owerri, Nigeria, 1996. ...
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... 46 (4), pp 14501452. DOI: 10.1021/jf970634y. Publication Date (Web): March 19, 1998. Copyright © 1998 American Chemical Society. ... by Udedibie and Carlini (1996, unpublished data) showed marked differences between Canavalia seeds... more
... 46 (4), pp 14501452. DOI: 10.1021/jf970634y. Publication Date (Web): March 19, 1998. Copyright © 1998 American Chemical Society. ... by Udedibie and Carlini (1996, unpublished data) showed marked differences between Canavalia seeds from Brazil and Nigeria in contents of ...
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Canatoxin (CNTX), the toxic protein purified from Canavalia ensiformis, has been shown to induce secretion from different cellular systems through a mechanism involving a lipoxygenase-mediated pathway. Here it is shown that CNTX causes... more
Canatoxin (CNTX), the toxic protein purified from Canavalia ensiformis, has been shown to induce secretion from different cellular systems through a mechanism involving a lipoxygenase-mediated pathway. Here it is shown that CNTX causes insulin release from isolated rat pancreatic islets. This effect is time and dose dependent, occurs in the absence as well in the presence of glucose, and is markedly reduced at lower temperatures (15 C). At 1-2 microM, the insulinotropic effect of CNTX is equivalent to that of 20 mM glucose, and the two responses are not additive. The stimulatory effect of CNTX is not caused by a toxic or lytic effect of the toxin on the islets, since islets once exposed to CNTX are able to respond a new insulinotropic stimulus. The phospholipase inhibitor mepacrine impairs insulin release induced by either CNTX or glucose. Indomethacin, an inhibitor of the cyclooxygenation of arachidonic acid, fails to affect insulin release, but two lipoxygenase inhibitors block it, and epinephrine reduces it. These data suggest that CNTX may act on islets through the same pathway as that used by glucose, with both effects being mediated by lipoxygenases.