Purification and partial characterization of the lectin from the marine green alga Caulerpa cupressoides (Vahl) C. Agardh

The marine green alga Caulerpa cupressoides was shown to contain a lectin which was purified by alpha -lactose-agarose affinity chromatography, followed by gel filtration on Bio Gel P-100. The lectin agglutinated trypsin-treated erythrocytes from humans and various animals, but was more active against human blood group A erythrocytes. The lectin was inhibited by lactose and some of its derivatives and was very strongly inhibited by the glycoprotein porcine stomach mucin. The molecular weight (MW) of Caulerpa cupressoides lectin, determined by gel filtration on a Bio-Gel P-100 column was 44,700, while by SDS-PAGE in the presence of 2-mercaptoethanol, the lectin exhibited a single protein band with a MW of 23,158, suggesting that the lectin is a dimeric protein. The lectin was heat stable losing part of its activity only at 80 degreesC and higher. The lectin showed high concentrations of glycine, acidic amino acids and serine and a low content of basic amino acids. The carbohydrate content of 11.05% suggested that the lectin is a glycoprotein.