Isolation and purification of a cytotoxic lectin from brown sea cucumber by affinity chromatography

Lectin activity was detected in the body walls and internal organs of brown, black and white sea cucumbers. The highest agglutination activity was detected in the brown sea cucumbers. The lectin obtained from the composite samples of brown sea cucumbers was therefore purified and characterized. Based on the results of hapten inhibition, fetuin was the only glycoside that prevented interaction of the lectin with erythrocytes. The lectin was further purified through (NH4)2 SO4 precipitation and affinity chromatography on fetuin agarose. The isolated lectin is nonblood-type specific as it agglutinated erythrocytes of all human blood types (A,B,AB, and O) and animal erythrocytes (those of horse and cattle). The lectin is classified as a complete type because it agglutinated untreated erythrocytes. The agglutinating activity of the lectin was enhanced by trypsination of the erythrocytes and addition of Ca2+. The lectin was stable at pH 2-12; its maximum agglutinating activity was observed at pH 10-11. Based on the results of gel chromatography, the lectin has an estimated molecular weights of 305 kilodalton (KD). Four bands with approximate molecular weights of 145 KD, 87 KD, 69 KD and 44 KD were detected through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The lectin is a glycoprotein containing 0.15% total sugar. Glucose and galactose were detected as component monosaccharides through high performance liquid chromatography (HPLC). Sea cucumber lectin has no antimicrobial activity against Escherichia coli. It transformed human lymphocytes into lymphoblasts, an indication of the lectin's mitogenic activity. The lectin likewise exhibited cytotoxicity against mouse cancer cells (Sarcoma T180) and human lung cancer cells (A549) at 5 ug/mL and 50 ug/mL, respectively