Purification and characterization of three lectins extracted from Cassia fistula seeds and effect of various physical and chemical agents on their stability

Three lectins designated as CSL-1, CSL-2 and CSL-3 were purified from Cassia fistula seeds by gel filtration on Sephadex G-50 followed by ion-exchange chromatography on DEAE cellulose and finally by affinity chromatography on Sepharose 4B. The molecular weights of the lectins CSL-1, CSL-2 and CSL-3, determined by gel filtration on Sephadex G-75 column were 37,000, 42,400 and 46,000, and by SDS gel electrophoresis were 37500, 42000 and 46500, respectively. All three lectins agglutinated rat red blood cells and the agglutination was inhibited specifically by galactose and galactose containing saccharide. The neutral sugar contents of the lectins, CSL-1, CSL-2 and CSL-3 were estimated to be 3.5, 3.1 and 2.0%, respectively. The sugar composition of the lectins was found to be galactose in CSL-1, galactose and glucose in CSL-2, and galactose and mannose in CSL-3. The lectins exhibited maximum hemagglutinating activities around pH 7.2 to 7.5 and at a temperature range of 20degrees to 35 degreesC. Biological activities of the lectins were abolished sequentially with the increase in concentration of acetic acid and denaturant solutions such as urea and guanidine-HCl.