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Biological effects induced by lectin isolated from the red algae (Bryothamnion triquetrum)
Buzzo, S.C.1; Fonseca, F.V.1; Carneiro, E.V.2; Boschero, A.C.2; Antunes, E.3; Morganti, R.P.3; Toyama, D.O.4; Cavada, B.S.5; K.S. Nascimento5; Sampaio, A.H.6; and Toyama, M.H.7
1-Departamento de Bioquímica, Inst. de Biologia, UNICAMP, Campinas-SP
2-Departamento de Fisiologia e Biofísica, Inst. de Biologia, UNICAMP, Campinas-SP.
3-Departamento de Farmacologia, Faculdade de Ciências Médicas, UNICAMP, Campinas-SP.
4-Faculdade de Ciências Biológicas, Exatas e Experimentais, Universidade Mackenzie, São Paulo-SP.
5-BioMolPep, Departamento de Bioquímica, Universidade Federal do Ceará, Fortaleza-CE.
6-Laboratório de Bioquímica Marinha, Departamento de Engenharia de Pesca, Universidade Federal do Ceará, Fortaleza-CE.
7-UNESP, Campus do Litoral Paulista, São Vicente-SP.
In this work we isolated the lectins Bt-D1 and Bt-D2, which are isoforms from the red alga Bryothamnion triquetrum using a new purification protocol based on the strong anion exchange chromatography. These lectins presented a molecular mass of 9KDa, four cystein residues and its hemagglutination activity is not inhibited by carbohydrates such as glucose, lactose and galactose. However in this study we used only Bt-D2 because we have this in a major quantity in our extract. In addition we evaluated the effect of this lectin on the pharmacological effects of the catalytically (D49, Cdcasca) and none catalytically (K49, bthtx-I) active PLA2 isolated from the Crotalus durissus cascavella and Bothrops jararacussu, respectively. In the case of the PLA2 from Crotalus durissus cascavella we used only the PLA2 subunit without crotapotin.
The platelet aggregation assay was made in washed platelets. Bt-D2 did not show significative action on platelets. The lectin strongly reduced the platelet aggregation: the catalytically PLA2 plus the lectin showed 59,6% of reduction on the aggregation if compared with this PLA2 alone, the none catalytically PLA2 plus the lectin showed 92,3% of reduction on the aggregation if compared with this PLA2 alone. The rat paw oedema assay showed a reduction of the effects of the PLA2 by the lectin too. The catalytically PLA2 treated with the lectin showed 12,5% of reduction on the volume of the paw if compared with this PLA2 alone, the none catalytically PLA2 showed 20% of reduction on the volume of the paw if compared with this PLA2 alone. The lectin alone showed a increase in the volume of the paw similar to the control with saline.
Also, this lectin inhibited the insulin secretion and modified the Ca2+ mobilization during the incubation of Bt-D2 with isolated pancreatic islets. The domain of secretory PLA2 was close of the catalytic site and these probably explain the inhibition of the enzymatic activity of isolated PLA2 by the isoform Bt-D2. These both results suggest an ability of the carbohydrate domain recognition (CDR) of the lectin Bt-D2 to interact specifically to the PLA2 receptor or the pancreatic β-cells. Finally we evaluated the secondary structure of this lectin using a CD spectra analysis, which revealed a predominant presence of randon coiled structure and little content of α-helix or β-sheet.
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