Abstract
A blood group non-specific hemagglutinin which recognizes N-acetyl chitosaccharides was isolated from the homogenate of cherry tomato (Lycopersion esculentum var. Cherry) by conventional ion exchange chromatographic techniques, and also by affinity chromatography on a chitin column. The purified cherry tomato lectin (LEcA) was a hydroxyproline-rich single polypeptide glycoprotein (Mr100, 000), containing 50% carbohydrate moiety (94% L-arabinose and 4% D-galactose). The carbohydrate-binding specificity of the purified lectin was studied by quantitative precipitation and hapten inhibition assay. This lectin was highly specific to β-(1→4) -linked N-acetyl glucosaminyl units. It strongly reacted with N-acetyl-chitobiose-BSA, but not with N-acetyl-glucosamine-BSA. The interaction of LEcA with thyroglobulin on GLISA (glycoprotein-lectin immunosorbent assay) was inhibited by N-acetyl-chitosaccharides, in the order [GlcNAc] 5 >[GlcNAc] 4 >[GlcNAc] 3 >[GlcNAc] 2, having approximately 194-times, 32-times and 5-times greater potency, respectively, than [GlcNAc] 2. The periodate-oxidized and reduced derivative of [GlcNAc] 4 and [GlcNAc] 5 were also good inhibitors, which showed similar inhibitory potency as the intact [GlcNAc] 2 and [GlcNAc] 3, respectively, strongly suggesting that LEcA recognizes internal N-acetyl-chitosaccharide sequences. LEcA appeared to resist the active transport of sugar to some extent, on the epidermal membrane of rat small intestinal, as examined by using the everted sac. The histochemical study by immunostaining using anti-LEcA antibodies visualized the localization of the lectin on the rat brush-border membrane, suggesting interaction of LEcA with the intestinal epidermal cell surface.
