Caracterização estrutural parcial e biológica de duas lectinas do gênero Canavalia

Abstract

Lectins are proteins that bind carbohydrates specifically and reversibly. The legume lectins represent the best studied and established group, from the point of view of physical-chemical and biological and structural, where a well-studied group of these proteins involves lectin obtained from members of the subtribe Diocleinae. Lectins Diocleinae have a high degree of structural similarity, but the same was not true regarding biological activities. This variability, as a rule, is in the detail that can be analyzed in structures based studies. In this context, multiple cardiovascular disease and inflammatory processes, particularly chronic and recurrent nature, arouse the interest of the scientific community because they require a wider range of drugs for therapeutic alternatives. In this sense, they become important research seeking new compounds with vasorelaxant and anti-inflammatory action. The present paper describes the partial structural and biological characterization of two lectins present in Canavalia virosa and Canavalia oxyphylla seeds, belonging to the family Leguminosae, subfamily Papilionoideae, Phaseoleae tribe, subtribe Diocleinae. The lectin from Canavalia virosa seeds (ConV) was purified in a single step by affinity chromatography on mannose-Sepharose 4B column. ConV strongly agglutinated rabbit erythrocytes and was inhibited by monosaccharide (D-mannose, D-glucose and α-methyl-D-manosídeo) and glycoproteins (fetuin and ovalbumin). SDS-PAGE revealed three bands, corresponding to three chains (α, β, γ and) confirmed by ESI mass spectrometry with masses of 25.480 ± 2 Da, 12.864 ± 1 Da and 12,633 ± 1 Da, respectively. The hemagglutination activity of ConV is great in pH 7.0 to 9.0, stable at a temperature of 80° C, and is not affected by EDTA. ConV showed no toxicity against Artemia sp. and relaxed the endothelized rat aorta, with the participation of the lectin domain. In our tests, the lectin immobilized on CNBr-Sepharose was able to bind 0.8 mg of ovalbumin by chromatography, allowing the use of ConV as a tool to capture and purification of glycoproteins. Moreover, the lectin from Canavalia oxyphylla (CoxyL) was purified in a single step by affinity chromatography on Sephadex G-50 column. SDS-PAGE showed that pure lectin consists of a major band of 30 kDa (α chain) and two minor components (β and γ chains) of 16 and 13 kDa, respectively. These data were further confirmed by mass spectrometry via electrospray ionization. Compared to the average molecular weight of the α chains, the partial amino acid sequence obtained corresponds to about 45% of the total sequence CoxyL. CoxyL showed hemagglutinating activity was specifically inhibited by monosaccharide (D-glucose, D-mannose and methyl-α-D-manosídeo) and glycoproteins (fetuin and ovalbumin). Furthermore, CoxyL proved to be heat stable at 60° C, and its activity is optimal at pH 7.0. CoxyL caused toxicity in Artemia sp. and induced paw edema in rats.