Concanavalin A from Canavalia ensiformis seeds (jack beans), (C08-0505-286)

Pure Canavalia ensiformis lectin (Con A) from Jackbean. Isolated by affinity chromatography on cross-linked dextran. Con A exists as a dimer below pH 5.0 and and at pH >7 it exists as a tetramer. Con-A is not a glycoprotein. The monomeric molecular weight of Con-A is 25,500. Con-A does not contain cysteine residues. Unlike most other lectins, Con-A is a metalloprotein and requires a transition metal ion, such as manganese, plus calcium ions for binding. Lectins are proteins or glycoproteins of non-immune origin that agglutinate cells and/or precipitate complex carbohydrates. Lectins are capable of binding glycoproteins even in presence of various detergents. The agglutination activity of these highly specific carbohydrate-binding molecules is usually inhibited by a simple monosaccharide, but for some lectins, di, tri, and even polysaccharides are required. Lectin are used in a wide variety of applications in vitro, including: blood grouping and erythrocyte polyagglutination studies, Mitogenic stimulation of lymphocytes, Lymphocyte subpopulation studies, Fractionation of cells and other particles, Histochemical studies of normal and pathological conditions. Con-A has been used to elucidate structural changes in the membrane surface of transformed cells. Con-A conjugates of antitumor drugs have been used in drug delivery systems in cultured cells. Con A is not blood group specific but has an affinity for terminal α-D-mannosyl and α-D-glucosyl residues. Ca2+ and Mn2+ ions are required for activity. Con A dissociates into dimers at pH 5.6 or below. Between pH 5.8 and pH 7.0, Con A exists as a tetramer; above pH 7.0 higher aggregates are formed. Con A exhibits mitogenic activity which is dependent on its degree of aggregation. Succinylation results in an active dimeric form which remains a dimer above pH 5.6. Con-A binds specifically to mannosyl and glucosyl residues of polysaccharides and glycoproteins. Unmodified hydroxyl groups at the C3, C4 and C6 positions of D-glucopyranosyl or D-mannopyranosyl rings may be essential for binding. Each subunit of Con-A contains one calcium ion and one manganese ion. Removal of these cations by dialysis under acidic conditions abolishes the carbohydrate-binding activity.