Characterization of the carbohydrate moiety of Clerodendron trichotomum lectins

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Abstract
Lectins were isolated from fruits and leaves of Clerodendron trichotomum by affinity chromatograpy on lactamyl‐Sepharose. The purified lectins (C. trichotomum agglutinin: CTA) were homogeneous on SDS/polyacrylamide gel electrophoresis, and the carbohydrate moiety was characterized by physicochemical and immuno‐chemical methods.The asparagine‐linked oligosaccharides were released by treatment with N‐oligosaccharide glycopeptidase (almond, EC 3.5.1.52) of peptic glycopeptides obtained from fruit CTA, and separated by gel filtration and thin‐layer chromatography. The structure of the predominant oligosaccharide was determined as Xylβ1 → 2 (Manα1 → 6)(Man α1 → 3)Manβ1 → 4GlcNAcβ1 → 4(Fucα1 → 3)GlcNAc by high‐performance liquid chroma‐tography, sugar analysis and 1H‐NMR spectroscopy.The reactivity of the carbohydrate moiety of CTA toward various lectins was studied. Fruit and leaf CTAs were applied to polyacrylamide gel electrophoresis, transferred to nitrocellulose sheets and detected with horseradish‐peroxidase‐conjugated lectins. Concanavalin A, lentil lectin, pea lectin, Vicia faba lectin and Ulex europeus agglutinin I, but not wheat germ lectin, bound to fruit CTA. The results indicate new binding properties of these plant lectins: (a) a β‐xylosyl residue substituted at C‐2 of the β‐mannosyl residue of N‐linked oligosaccharide does not affect the binding with mannose‐specific lectins, (b) lentil, pea and Vicia faba lectins can bind to N‐linked oligosaccharides containing an α‐l‐fucosyl residue attached to C‐3 of the asparagine‐linked N‐acetyl‐D‐glucosamine residue, and (c) Ulex europeus agglutinin I can bind to the (α1 → 3)‐linked fucose residue of the N‐linked oligosaccharide.