Isolation and Physicochemical Characterization of Momordica Balsamina Seed Lectin and Its Effects on Human Commercial Cancer Cell Lines

Abstract

The aim of the present study was to isolatation, purification and characterization of Momordica balsamina seeds lectin (MbSL) and study the possible modulating effects of the purified lectin on four types of commercial cancer cell lines. A season fresh of Momordica balsamina fruit seeds were brought from urban areas of Sudan (Gadrif and north Kurdofan states). The lectin was isolated from saline extract by affinity chromatography on alpha agarose lactose matrix. The lectin content which was determined by the method of Lowry was about 1200 mg/ 100 g dry flour. MbSL agglutinated all types of human red blood cells (RBCs) with preference toward the O blood group. The lectin also agglutinated mouse, donkey and cow red blood cells but showed no effect on goat erythrocytes. Lactose was the most potent inhibitor of MbSL hemagglutinating activity, minimal inhibitory concentration (MIC) = 25 mM, followed by galactose, MIC=50 mM, and then arabinose, MIC= 100 mM. The native molecular weight of lectin detected by gel filtration chromatography was 81 kDa and when examined by SDS-PAGE it was found to be composed of a single subunit of molecular mass around 30 kDa. The search for sequential identities of the purified lectin was carried out by using BLAST (h.ttp://blast.ncbi.nlm.nih.gov/Blast.cgi), and the N-terminal of the lectin shared major similarities with reported Momordica charantia lectin 1(MCL 1) and found to be a ribosome inactivating protein type II (RIP II). The activity of the lectin remained stable in the pH range 2-12, and it remained stable below 50 ºC without losing its hemagglutinating activity. Above 50 ºC lectin activity was gradually lost and was totally inactivated at 90 ºC. MbSL activity slightly decreased against denaturation with urea, with significant drop at 3M. After evaluation of Cytotoxicity of the purified lectin using the MTT Assay in AGS (Human Gastric Adenocarcinoma), MKN45 (Human Gastric Cancer), U87-MG (Human Glioblastoma) and ECV-304 (Human Urinary Bladder Carcinoma) cell lines, the lectin showed no inhibitory effect on the growth of different types of human commercial cancer cell lines. This identified MbSL as a nontoxic ribosome inactivating protein type II. In conclusion: a lactose-binding lectin from seeds of Momordica balsamina medicinal plant shares a high degree of similarity with other Cucurbitaceae family lectins in term of their physicochemical features including sugar specificity, effect of pH and temperature and urea on lectin stability. MbSL was found to be one of nontoxic RIP II and had no effect on the growth of four types of human commercial cancer cell lines chosen to study the modulating effect of the purified lectin on it.