Proceeding
Carbohydrate-binding Properties of the Purified Cherry Tomato (Lycopersion esculentum var. Cherry) and Immunohistochemical Application
1996 Volume 13 Pages 135-143
Details
1996 Volume 13 Pages 135-143
A blood group non-specific hemagglutinin which recognizes N-acetyl chitosaccharides was isolated from the homogenate of cherry tomato (Lycopersion esculentum var. Cherry), which showed the highest hemagglutinating activity among genetically diverse 28 kinds of tomatoes, 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 (Mr 100,000), 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 immunosorbe川 assay)was inhibited by N-acetyl-chitosaccharides, in order, [GlcNAc]5 > [GlcNAc]4 > [GlcNAc]3 > [GlcNAch having approximately 194-times, 32-times and 5-times greater potency, respectively, than [GlcNAc]2. The per iodate一oxidizedand 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 sequence.
Although, LEcA showed non-inhibitory activity for sugar-hydrolytic enzymes from animal digestive tract, LEcA appeared to inhibit 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. This strongly suggested the cherry tomato lectin can bind to either the intestinal epidermal cell surface or the secreted glycoprotein which contain β(1→4) -linked N-acetyl-glucosaminyl sugar chains although it may not affect to the nutritional function.
