RESUMO
A novel lectin, HGA-2, was isolated from the sea cucumber Holothuria grisea. The protein was isolated by a single chromatographic step using a column of Guar Gum as affinity. HGA-2 showed an apparent molecular mass of 17 kDa and 34 kDa under reducing and nonreducing conditions, respectively. The hemagglutinating activity was specific for rabbit erythrocytes, showing no activity for human blood A, B and O. Its hemagglutinating activity was inhibited by carbohydrates containing galactose, with higher affinity for GalNAc and glycoprotein porcine stomach mucin (PSM). HGA-2 was stable at pH 6-10, significantly declining at pH 5 and a temperature of 40°C, with its activity being abolished at 100 °C. The HGA-2 protein was found to be Ca(2+)-dependent; it was highly toxic against Artemia nauplii and able to recognize and agglutinate cells of Escherichia coli. Amino acid sequences of tryptic peptides of HGA-2 strongly suggest that HGA-2 is a member of the C-type lectin family.
Assuntos
Aglutininas/química , Aglutininas/metabolismo , Escherichia coli/metabolismo , Galactosídeos/metabolismo , Holothuria/química , Lectinas/química , Lectinas/metabolismo , Aglutininas/isolamento & purificação , Aglutininas/toxicidade , Sequência de Aminoácidos , Animais , Hemaglutinação , Testes de Hemaglutinação , Humanos , Concentração de Íons de Hidrogênio , Íons , Lectinas/isolamento & purificação , Lectinas/toxicidade , Lectinas Tipo C , Dados de Sequência Molecular , Coelhos , Alinhamento de Sequência , TemperaturaRESUMO
The effect of pre-soaking raw seed beans upon detoxification and the biological quality of its protein were evaluated. In whole raw seed beans (Phaseolus vulgaris) var. "tórtola", the net protein utilization (NPU), true digestibility and hemagglutinin titer were determined after 60', 90' and 120' of heat treatment, with and without 14 hours of pre-soaking. It is concluded that soaking prior to cooking is not necessary to eliminate the toxicity of dry beans, but that it does contribute to the softening of seeds and reduction of cooking time. The hemagglutinin levels of six commercial bean flours were evaluated, concluding that almost all of them presented toxic levels. The effect of the cooking methods upon the toxicity of bean flours was studied. Two raw bean flours, var. "tórtola" and "burro" at 10% and 20%, were cooked employing different boiling times (5, 10, 15 and 30'). The two raw samples contained high hemagglutinin levels which were inactivated at 10% with 10' cooking. The presence of toxic levels was detected at 20% after 15' cooking and these were eliminated at 30' of cooking.