Affinity chromatography of a lectin from Robinia pseudoacacia L. and demonstration of lectins in sieve-tube sap from other tree species.

A carbohydrate-binding protein in the sievetube sap of Robinia pseudoacacia L. was isolated by affinity chromatography on D-galactosamine coupled to CH-Sepharose 4B. The yield of the purified protein was 41,3 μg/ml of sieve-tube sap or 5,7% of the total protein. In disk electrophoresis at an alkaline and acidic pH the lectin appeared to be homogenous. It has a molecular weight of about 100,000 and consists of four types of subunits (mol wt. 70,000, 60,000, 32,500, 25,000). The complex formation between the Robinia lectin and erythrocytes is inhibited by simple sugars, especially N-acetyl-D-galactosamine, but not by glycoproteins containing N-acetyl-glucosamine or by a partial hydrolysate of chitin. Sieve-tube sap of 63 different species out of 21 families were examined for their lectin-activity. With the exception of the species of the families Aceraceae and Oleaceae, all analyzed species agglutinated trypsinized rabbit erthrocytes. 15 species were examined for their sugar specifity. Their lectin-activity was not inhibited by simple sugars, but by glycoproteins containing N-acetyl-glucosamine and by a partial hydrolysate of chitin. The same results was found for the lectin from the phloem exudate of Cucurbita pepo.