Extração da lectina da folha de mandioca (Manihot esculenta Crantz) e o efeito de cátions divalentes na atividade hemaglutinante

Abstract

Lectins are carbohydrates binding proteins, capable of agglutinating erythrocytes, which can act as anti-nutritional factors. The isolation of these toxic proteins is interesting both for its anti- nutritional action and for its application in biotechnology. Some lectins need the presence of divalent ions to express hemagglutinating activity (AH). The objective of this work was to investigate different methods of extracting lectins from cassava leaf flour (CLF) and to evaluate the effect of the ions Ca2+ and Mn2+ on the AH. Protein extraction tests were performed utilizing two extractors, water and saline solution (0.15 mol.L-1, NaCl pH 7.4), under four extraction times, 15, 60, 120, and 180 minutes. To evaluate the effect of the ions Ca2+ and Mn2+ on the AH of CLF lectin, the protein extract was dialyzed against EDTA and the AH was determined. The effect of the cations upon the agglutination of red blood cells was also evaluated individually. The protein extraction method utilizing water as extractor under 15 minutes was the most suitable. No loss of AH was found in the absence of the ions. The cations Ca2+ (5 mmol.L-1), Mn2+ (1, 3 and 5 mmol.L-1), and the mixture of both under the same concentrations provoked agglutination of red blood cells in the absence of lectin.