Caracterização estrutural e biológica das lectinas de sementes de Parkia biglobosa (Jacq.) Benth e Vatairea guianensis Aublet.

Abstract

Lectins are defined as structurally heterogeneous proteins of non-immune origin, possessing at least one non-catalytic domain by which they reversibly bind to specific mono- or oligosaccharides. By deciphering the codes present in the glycan structure, lectins are attracting increasing interest in biotechnology. The most studied group of carbohydrate-binding proteins consists of lectins purified from species of the Leguminosae family. Among the studies of the lectins from Leguminosae. many are focused on members of the Papilionoideae subfamily, while investigations of lectins of the other two subfamilies, Caesalpinioideae and Mimosoideae, are scarce. Even within the subfamily Papilionoideae, the vast majority of studies focus on lectins from Phaseoleae and Vicieae tribes, while the other tribes of this subfamily are still poorly explored. In this context, this work describes the structural and biological characterization of two new lectins purified from seeds of Parkia biglobosa (Mimosoideae subfamily, tribe Parkiae) and Vatairea guianensis Aublet (subfamily Papilionoideae, tribe Dalbergieae). P. biglobosa seeds (subfamily Mimosoidae) possess mannose/glucose-specific lectin (PBL) that was purified by affinity chromatography on a Sephadex G-100 column. PBL is composed by a single nonglycosylated polypeptide chain of three tandemly arranged jacalin-related domains and showed important antinociceptive activity associated to the inhibition of inflammatory process. PBL was crystallized and the data produced in the X-ray diffraction experiments will enable the future resolution three-dimensional structure of this protein. With respect to the N-acetyl-D-galactosamine/D-galactose specific lectin present in the V. guianensis seeds (VGL) was demonstrated that this protein presents high similarity in primary structure to other lectins from evolutionarily related plants, such as VML and lectins belonging to the Sophoreae tribe. VGL exhibits vasorelaxant activity in contracted rat aortas, an effect that is strictly dependent on the endothelium and involves NO and the lectin domain.