RESUMO
L-canavanine, the toxic guanidinooxy analogue of L-arginine, is the product of plant secondary metabolism. The need for a detoxifying mechanism for the producer plant is self-evident but the larvae of the bruchid beetle Caryedes brasiliensis, that is itself a non-producer, have specialized in feeding on the Lcanavanine-containing seeds of Dioclea megacarpa. The evolution of a seed predator that can imitate the enzymatic abilities of the host permits us to address the question of whether the same problem of amino acid recognition in two different kingdoms has been solved by the same mechanism. A discriminating arginyl-tRNA synthetase, detected in a crude C. brasiliensis larval extract, was proposed to be responsible for insect's ability to survive the diet of L-canavanine (Rosenthal, G. A., Dahlman, D. L., and Janzen, D. H. (1976) A novel means for dealing with L-canavanine, a toxic metabolite. Science 192, 256e258). Since the arginyl-tRNA synthetase of at least three genetic compartments (insect cytoplasmic, insect mitochondrial and insect gut microflora) may participate in conferring L-canavanine resistance, we investigated whether the nuclear-encoded C. brasiliensis mitochondrial arginyl-tRNA synthetase plays a role in this discrimination. Steady state kinetics of the cloned, recombinant enzyme have revealed and quantified an amino acid discriminating potential of the mitochondrial enzyme that is sufficient to account for the overall L-canavanine misincorporation rate observed in vivo. As in the cytoplasmic enzyme of the L-canavanine producer plant, the mitochondrial arginyl-tRNA synthetases from a specialist seed predator relies on a kinetic discrimination that prevents L-canavanine misincorporation into proteins.
Assuntos
Arginina-tRNA Ligase/metabolismo , Canavanina/toxicidade , Núcleo Celular/metabolismo , Mitocôndrias/metabolismo , Aminoácidos/genética , Animais , Arginina-tRNA Ligase/química , Arginina-tRNA Ligase/genética , Canavanina/química , Núcleo Celular/genética , Besouros/efeitos dos fármacos , Besouros/enzimologia , Besouros/metabolismo , Costa Rica , Dioclea/química , Cinética , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Mitocôndrias/genéticaRESUMO
Se realizó un estudio comparativo entre la asimilación de la D-prolina y el crecimiento en medio canavanina-glicina-azul de bromotimol (CGB) utilizados para la clasificación de las variedades de Cryptococcus neoformans. En las 86 cepas estudiadas, 100 por ciento de coincidencia entre ambos métodos, permitió afirmar que 95,34 por ciento pertenecían a la var. neoformans y el resto (4,65 por ciento) a la var. gattii. Los resultados obtenidos corroboraronn que todos los aislamientos clínicos autóctonos, hasta el presente, corresponden a la var. neoformans y permitieron sugerir el uso de la D-prolina para la evaluación inicial de las cepas, como un método alternativo y sencillo que presentó, en estas condiciones, alta coincidencia con el método de referencia (crecimiento en CGB)
Assuntos
Azul de Bromotimol , Canavanina , Criptococose , Cryptococcus neoformans , ProlinaRESUMO
Se conocen 2 variedades de cryptococcus neoformans y 5 serotipos: cryptococcus neoformans var. neoformans (serotipos A,D y AD), usualmente aislados a partir de muestras clínicas, encontrándose cryptococcus neoformans var. neoformans serotipo A, con mayor incidencia en pacientes con SIDA; cryptococcus neoformans var. gattii (serotipos B y C), los cuales son aislados menos frecuentemente principalmente en pacientes VIH seronegativos y excepcionalmente han sido asociados con SIDA. Se estudiaron 43 cepas de cryptococcus neoformans. El medio de canavanina-glicina-azul de bromotinol (CGB) permite diferenciar en crytococcus la variedad gattii de la variedad neoformans. Nuestro estudio refleja que las 2 cepas (4,65 por ciento) de cryptococcus neoformans var. gattii, obtenidas a partir del aislamiento de muestras de líquido cefalorraquídeo, procedían de una paciente con inmunodeficiencia celular y humoral catalogada como ideopática, y de un paciente con SIDA, asociación rara vez reportada. Son escasos los estudios epidemiológicos de esta micosis en Venezuela, y pocos hacen identificación más allá de la especie, por lo cual es dificil comparar nuestros resultados
Assuntos
Azul de Bromotimol , Canavanina , Cryptococcus neoformans , Glicina , Microbiologia , VenezuelaRESUMO
1. Intestinal brush border membrane vesicles (BBMV) were prepared from 3-week-old broiler chickens. 2. Electron microscopy of the BBMV fraction showed single membrane vesicles of different sizes with no electron dense material inside. No other organelles were observed. The sucrase and maltase activities were enriched by factors of 16 and 18, respectively, in the BBMV fraction in comparison with the homogenate. On the other hand, the Na+/K+-ATPase sensitivity to ouabain was increased by a factor of 0.8. 3. The BBMV showed a maximum L-[14C]-arginine uptake (944.9 +/- 22.9 pmoles/mg protein) at 45 s and thereafter it declined slowly. In the presence of 0.5 mM L-canavanine, the L-[14C]-arginine uptake by BBMV was reduced by 43.6% at 45 s. 4. It is concluded that L-canavanine inhibits L-arginine Na+-dependent transport across the enterocyte apical membrane in a highly purified intestinal BBMV from broiler chickens.
Assuntos
Arginina/metabolismo , Canavanina/farmacologia , Absorção Intestinal/efeitos dos fármacos , Mucosa Intestinal/metabolismo , Microvilosidades/metabolismo , Animais , Arginina/antagonistas & inibidores , Biomarcadores , Radioisótopos de Carbono , Fracionamento Celular , Galinhas , Mucosa Intestinal/efeitos dos fármacos , Cinética , Microvilosidades/efeitos dos fármacos , Microvilosidades/ultraestrutura , Técnica de Diluição de RadioisótoposRESUMO
Arginine kinase catalyzes the transphosphorylation between phosphoarginine and ADP. Phosphoarginine is involved in temporal ATP buffering and inorganic phosphate regulation. Trypanosoma cruzi arginine kinase phosphorylates only L-arginine (specific activity 398.9 x mUE-min(-1) x mg(-1)), and is inhibited by the arginine analogs, agmatine, canavanine, nitroarginine, and homoarginine. Canavanine and homoarginine also produce a significant inhibition of the epimastigote culture growth (79.7% and 55.8%, respectively). Inhibition constants were calculated for canavanine and homoarginine (7.55 and 6.02 mM, respectively). In addition, two novel guanidino kinase activities were detected in the epimastigote soluble extract. The development of the arginine kinase inhibitors of T. cruzi could be an important feature because the phosphagens biosynthetic pathway in trypanosomatids is different from the one in their mammalian hosts.
Assuntos
Arginina Quinase/antagonistas & inibidores , Arginina/análogos & derivados , Inibidores Enzimáticos/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Trypanosoma cruzi/enzimologia , Animais , Arginina/metabolismo , Arginina/farmacologia , Canavanina/farmacologia , Meios de Cultura , Guanidinas/metabolismo , Homoarginina/farmacologia , Fosforilação , Fosfotransferases/metabolismo , Trypanosoma cruzi/crescimento & desenvolvimentoRESUMO
Introducción. Para estudiar la toxicidad y el efecto metabólico de la canavanina en animales o plantas se depende de la disponibilidad de métodos sensibles, específicos y rápidos de análisis. Materiales y métodos. Se desarrolló un método para medir la concentración de L-canavanina por cromatografía líquida en fase reversa utilizando DABS-C1 como agente de derivación y se compararon los resultados con aquellos obtenidos por colorimetría por el método de Rosenthal. Cinco muestras de canavalia fueron utilizadas para validar la técnica. Resultados y discusión. La derivación con DABS-C1 permitió la determinación de éste aminoácido sin interferencia con otros aminoácidos. No se encontraron diferencias entre las concentraciones de L-canavanina en granos de Canavalia ensiformis cuando se midió por estos 2 métodos. El análisis colorimétrico puede ser empleado como una herramienta confiable de primera elección. Debido al alto costo que involucra el análisis por HPLC deberá ser empleado cuando exista evidencia de interferencia en el método colorimétrico de compuesto y/o metabolitos presentes en la muestra
Assuntos
Canavanina , Colorimetria , Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , EspectrofotometriaRESUMO
Se realizó la caracterización del grano de cinco genotipos de Canavalia ensiformis, mediante la determinación de la composición química proximal, presencia de factores antinutricionales (Canavalia y título hemaglutinante) y digestibilidad in vitro. Los genotipos estudiados fueron: Original, Yaracuy, Valle de la Pascua, U-02 y Tovar. Los resultados de la composición química proximal mostraron diferencias significativas entre los genotipos a excepción de la humedad, encontrándose los siguientes promedios: Proteína: 31,37 por ciento, fibra: 8,10 por ciento: cenizas: 2,93 por ciento, grasa: 2,97 por ciento y humedad: 11,68 por ciento. El contenido de canavanina de los genotipos fue variable, oscilando los valores entre 2,02 a 4,86 por ciento presentando el genotipo u-02 el valor mayor, respocto al título hemaglutinante varió entre +2 y +5. La digestibilidad proteica in vitro de las harinas arrojó diferencias signifacativas entre los genotipos, la cual varió entre 47,51 por ciento y 51,84 por ciento, valores muy por debajo al mostrado por la caseína (97,3 por ciento)
Assuntos
Canavanina/análise , Concanavalina A , Grão Comestível/química , Grão Comestível/classificação , Fabaceae , Farinha/classificação , Proteínas Alimentares , VenezuelaRESUMO
The tobacco budworm, Heliothis virescens (Noctuidae), a destructive insect pest, is remarkably resistant to L-canavanine, L-2-amino-4-(guanidinooxy)butyric acid, an arginine antimetabolite that is a potent insecticide for nonadapted species. H. virescens employs a constitutive enzyme of the larval gut, known trivially as canavanine hydrolase (CH), to catalyze an irreversible hydrolysis of L-canavanine to L-homoserine and hydroxyguanidine. As such, it represents a new type of hydrolase, one acting on oxygen-nitrogen bonds (EC 3.13.1.1). This enzyme has been isolated from the excised gut of H. virescens and purified to homogeneity; it exhibits an apparent Km value for L-canavanine of 1.1 mM and a turnover number of 21.1 micromol x min(-1)x micromol(-1). This enzyme has a mass of 285 kDa and is composed of two subunits with a mass of 50 kDa or 47.5 kDa. CH has a high degree of specificity for L-canavanine as it cannot function effectively with either L-2-amino-5-(guanidinooxy)pentanoate or L-2-amino-3-(guanidinooxy)propionate, the higher or lower homolog of L-canavanine, respectively. L-Canavanine derivatives such as methyl-L-canavanine, or L-canaline and O-ureido-L-homoserine, are not metabolized significantly by CH.
Assuntos
Canavanina/metabolismo , Canavanina/toxicidade , Hidrolases/metabolismo , Inseticidas/toxicidade , Mariposas/fisiologia , Acetona , Sequência de Aminoácidos , Sulfato de Amônio , Animais , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Sistema Digestório/enzimologia , Guanidinas/metabolismo , Homosserina/metabolismo , Hidrolases/química , Hidrolases/isolamento & purificação , Hidroxilaminas , Resistência a Inseticidas , Cinética , Larva , Dados de Sequência Molecular , Mariposas/enzimologia , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/isolamento & purificaçãoRESUMO
This study evaluated the raw meals from grains of five genotypes of Canavalia ensiformis, by means of the chemical composition, the presence of antinutritional factors (Canavanine and hemaglutination activity) and in vitro protein digestibility. The genotypes studied were: Original, Yaracuy, Tovar, Valle de la Pascua and U-02. The results of chemical composition, showed significance difference between them, except moisture content, found the following average values: Protein 31.37%, fiber: 8.10%, ash: 2.93% and moisture: 11.68%. The canavanine content of the genotypes was variable oscillating between 2.02 and 4.86%, the genotype U-02 presented the higher value, respect to the hemaglutination title changed between: +2 and +5. The in vitro protein digestibility of the raw meals showed significance differences between the genotype, it changed between 47.51% and 51.84%, these values were lower than the casein (97.3%).
Assuntos
Canavanina/análise , Concanavalina A/análise , Fabaceae/química , Farinha/análise , Plantas Medicinais , Urease/análise , Análise de Variância , Fabaceae/genética , Genótipo , Lectinas de PlantasRESUMO
Precooked flours obtained five Canavalia ensiformis varieties were prepared by dehydration in double drums. On a dry matter basis, significant differences (P < 0.05) among varieties were detected for crude protein content (25 to 30%), starch (36 to 40%) and dietary fiber (13 to 15%). Hemagglutinins were eliminated as result of the high temperature (146 degrees C/4 min) employed during the drying process. Similar results were not obtained for trypsin inhibitors and canavanine considering that small amounts of these compounds remained in the precooked flours prepared from canavalia seeds. A 10% decrease in available lysine was observed. Biological assays yielded Protein Efficiency Ratio (PER) values of 0, 8-1 and Neat Proteic Relation (NPR) values of 2-3-2.6. True digestibility of protein values were improved from 87 to 90%. All cultivars had similar starch digestive utilization coefficient (96%) and starch fraction (4%) resistant to enzymatic hydrolysis in the rat digestive tract.
Assuntos
Fabaceae , Farinha , Valor Nutritivo , Plantas Medicinais , Animais , Canavanina/isolamento & purificação , Fabaceae/metabolismo , Feminino , Farinha/análise , Humanos , Proteínas/metabolismo , Ratos , Ratos Wistar , Amido/metabolismo , Inibidores da Tripsina/análise , Inibidores da Tripsina/isolamento & purificaçãoRESUMO
Precooked flours obtained five Canavalia ensiformis varieties were prepared by dehydration in double drums. On a dry matter basis, significant differences (P < 0.05) among varieties were detected for crude protein content (25 to 30 percent), starch (36 to 40 percent) and dietary fiber (13 to 15 percent). Hemagglutinins were eliminated as result of the high temperature (146 degrees C/4 min) employed during the drying process. Similar results were not obtained for trypsin inhibitors and canavanine considering that small amounts of these compounds remained in the precooked flours prepared from canavalia seeds. A 10 percent decrease in available lysine was observed. Biological assays yielded Protein Efficiency Ratio (PER) values of 0, 8-1 and Neat Proteic Relation (NPR) values of 2-3-2.6. True digestibility of protein values were improved from 87 to 90 percent. All cultivars had similar starch digestive utilization coefficient (96 percent) and starch fraction (4 percent) resistant to enzymatic hydrolysis in the rat digestive tract
Assuntos
Humanos , Animais , Feminino , Ratos , Fabaceae , Farinha , Valor Nutritivo , Canavanina/isolamento & purificação , Fabaceae/metabolismo , Farinha/análise , Proteínas/metabolismo , Ratos Wistar , Amido/metabolismo , Inibidores da Tripsina/análise , Inibidores da Tripsina/isolamento & purificaçãoRESUMO
The purpose of this work was to collect the main information from the literature about the biotyping of Cryptococcus neoformans. The more up-to date research concerning the epidemiology of cryptococcosis comprising quite a few articles, mainly after the advent of AIDS, was also reviewed. The Cryptococcus neoformans varieties neoformans and gattii are well defined biochemically nowadays chiefly through the C.G.B. medium, according to Kwon-Chung et al. (1982). The isolation of C. neoformans var. gattii from flowers and leaves of Eucalyptus camaldulensis and Eucalyptus tereticornis, specially in Australia, through the works of Ellis & Pfeiffer (1990) and Pfeiffer & Ellis (1992) permitted very interesting epidemiological investigations on C. neoformans, a capsulated yeast by which Sanfelice, in Italy (1894; 1895) attracted attention of medical class. Busse, in 1894, described the first human case of cryptococcosis under the presentation of a bone lesion simulating sarcoma. In this paper, the Brazilian researchers focused on this subject were pointed out, followed by the Author's experience with the C.G.B. medium (L-canavanine, glycine and bromothymol blue) proposed by Kwon-Chung et al. (1982) with very good results. It was possible with such medium the study of 50 C.N.S. liquor samples, being 39 from AIDS patients (78) and 11 from non-AIDS ones (22). Thirty-seven out of the 39 HIV-positive patients (74) were identified as C. neoformans var. gattii. From the negative HIV, 8 (16) were classified as C. neoformans var. neoformans and 3 (6) as C. neoformans var. gattii. We could not perform the serotyping of the above referred samples. It is evident anyway that in Brazil there exist both varieties gattii and neoformans, agents of neurocryptococcosis, including AIDS patients. The importance of neurocryptococcosis, mainly among AIDS patients, is stressed here, showing once more the value of C.G.B. medium in the typing of C. neoformans in its two varieties. Also, it is of relevant importance the demonstration that some species of eucalyptus may act as "host-trees" of C. neoformans var. gattii.
Assuntos
Animais , Criptococose , Cryptococcus neoformans , Azul de Bromotimol , Canavanina , Criptococose , Cryptococcus neoformans , Meios de Cultura , Glicina , SorotipagemRESUMO
The purpose of this work was to collect the main information from the literature about the biotyping of Cryptococcus neoformans. The more up-to date research concerning the epidemiology of cryptococcosis comprising quite a few articles, mainly after the advent of AIDS, was also reviewed. The Cryptococcus neoformans varieties neoformans and gattii are well defined biochemically nowadays chiefly through the C.G.B. medium, according to Kwon-Chung et al. (1982). The isolation of C. neoformans var. gattii from flowers and leaves of Eucalyptus camaldulensis and Eucalyptus tereticornis, specially in Australia, through the works of Ellis & Pfeiffer (1990) and Pfeiffer & Ellis (1992) permitted very interesting epidemiological investigations on C. neoformans, a capsulated yeast by which Sanfelice, in Italy (1894; 1895) attracted attention of medical class. Busse, in 1894, described the first human case of cryptococcosis under the presentation of a bone lesion simulating sarcoma. In this paper, the Brazilian researchers focused on this subject were pointed out, followed by the Author's experience with the C.G.B. medium (L-canavanine, glycine and bromothymol blue) proposed by Kwon-Chung et al. (1982) with very good results. It was possible with such medium the study of 50 C.N.S. liquor samples, being 39 from AIDS patients (78%) and 11 from non-AIDS ones (22%). Thirty-seven out of the 39 HIV-positive patients (74%) were identified as C. neoformans var. gattii. From the negative HIV, 8 (16%) were classified as C. neoformans var. neoformans and 3 (6%) as C. neoformans var. gattii. We could not perform the serotyping of the above referred samples. It is evident anyway that in Brazil there exist both varieties gattii and neoformans, agents of neurocryptococcosis, including AIDS patients. The importance of neurocryptococcosis, mainly among AIDS patients, is stressed here, showing once more the value of C.G.B. medium in the typing of C. neoformans in its two varieties. Also, it is of relevant importance the demonstration that some species of eucalyptus may act as "host-trees" of C. neoformans var. gattii.
Assuntos
Criptococose/epidemiologia , Cryptococcus neoformans/classificação , Animais , Azul de Bromotimol , Canavanina , Criptococose/fisiopatologia , Cryptococcus neoformans/isolamento & purificação , Meios de Cultura , Glicina , SorotipagemRESUMO
There were made four nutrition experiments using pork in growing process, with an approximate weight of 14.2 kilograms. In each experiment, it was made a substitution in equals parts of corn flour and soy flour for raw Canavalia flour or processed through alkaline storage, autoclaved or extrusion. In the first three experiments, the substitution level of raw Canavalia (RC), stored in alkaline environment (CAMA) or autoclave (CA) were: 0, 5, 10 and 15%. In the fourth one, the including levels of Canavalia Extruida were: 0, 7.5 and 15%. The raw Canavalia as the Extruida drastically reduced the pork's growth. The Canavalia flour autoclaved (121 degrees C/15 psi/90 min) substantially improved the animal answers, even though the growth in all the substitution levels were lower than the one observed in the original portion. The storage of the beans in alkaline environment, made possible better productive behavior in the animals, and it didn't observe differences (p < 0.01) to increase the witness weight, at the substitution level or 5%. The pork's answer to the Canavalia toxin was manifested in the first term, by a drastic reduction in the voluntary consumption of foods. As a whole, the results indicated that none of the methods used were effective to eliminate or to minimize the toxic effects in the raw Canavalia over the productive behavior of growing pork.
Assuntos
Ração Animal , Fabaceae , Farinha , Manipulação de Alimentos/métodos , Proteínas de Plantas , Plantas Medicinais , Suínos/crescimento & desenvolvimento , Toxinas Biológicas , Aminobutiratos/análise , Ração Animal/análise , Animais , Canavanina/análise , Concanavalina A/análise , Fabaceae/química , Conservação de Alimentos/métodos , Hemaglutinação , Temperatura Alta , Concentração de Íons de Hidrogênio , Lectinas/análise , Extratos Vegetais , Lectinas de Plantas , Plantas Tóxicas/química , Sementes/químicaAssuntos
Animais , Ração Animal , Fabaceae , Farinha , Manipulação de Alimentos/métodos , Suínos/crescimento & desenvolvimento , Aminobutiratos/análise , Ração Animal/análise , Canavanina/análise , Concanavalina A/análise , Resumo em Inglês , Conservação de Alimentos/métodos , Hemaglutinação , Temperatura Alta , Concentração de Íons de Hidrogênio , Lectinas/análise , Fabaceae/química , Extratos Vegetais , Plantas Tóxicas/química , Sementes/químicaRESUMO
Estudou-se o efeito de alfafetoproteína (AFP) sobre a proliferaçäo de linfócitos periféricos humanos estimulados por fitohemaglutinina (PHA), concanavalina A (Con A), pokeweed mitogênio (PWM) e por células alogênicas em culturas mistas de linfócitos, ao medir-se e comparar-se a incorporaçäo de timidina triciada (parâmetros de crescimento celular) em culturas contendo AFP humanas purificada e em culturas sem a proteína (controles). Nenhuma alteraçäo quantitativa na reatividade linfocitária foi verificada nas culturas com AFP