Banana lectin is unique in its recognition of the reducing unit of 3-O-β-glucosyl/mannosyl disaccharides: A calorimetric study

Abstract

The binding of banana lectin (BanLec) to laminaribiose (Glcβ1,3Glc) and a series of novel synthetic analogues was measured by titration calorimetry to assess the contribution of the hydroxyl groups of the reducing glycosyl moiety and its 3-O-β-substituent to binding. Key areas of interaction involved the 1, 2, and 6 positions of the reducing-terminal hexose unit. The α-anomeric configuration of the reducing hexose was strongly favored over the β-anomer. The 2-hydroxyl in the axial position (mannose) also enhanced binding, whereas the 6-hydroxymethyl group was essential, because xylopyranose in the reducing position was inactive. The 3-O-β-glucosyl unit of methyl α-laminaribioside could be replaced by any of its monodeoxy derivatives. However, the 49-deoxy derivative or axial hydroxy (galactosyl) substitution was somewhat detrimental to binding. 3-O-substitution with the (S)tetrahydropyranyl ring or a benzyl group had similar effect as 4′-deoxyglucosyl substitution. Surprisingly, p-nitrobenzyl or β-xylosyl 3-0-substitution greatly enhanced binding of the reducing glucosyl or mannosyl derivative. Chemical syntheses of a number of novel disaccharides and analogues prepared for this study are described. © The Authors 2005. Published by Oxford University Press. All rights reserved.