Carbohydrate binding properties of banana (Musa acuminata) lectin

Examination of lectins of banana (Musa acuminata) and the closely related plantain (Musa spp.) by the techniques of quantitative precipitation, hapten inhibition of precipitation, and isothermal titration calorimetry showed that they are mannose/glucose binding proteins with a preference for the a-anomeric form of these sugars. Both generate precipitin curves with branched chain a-mannans (yeast mannans) and a-glucans (glycogens, dextrans, and starches), but not with linear a-glucans containing only a1,4and a1,6glucosidic bonds (isolichenan and pullulan). The novel observation was made that banana and plantain lectins recognize internal a1,3-linked glucosyl residues, which occur in the linear polysaccharides elsinan and nigeran. Concanavalin A and lectins from pea and lentil, also mannose/glucose binding lectins, did not precipitate with any of these linear a-glucans. This is, the authors believe, the first report of the recogniton of internal a1,3±glucosidic bonds by a plant lectin. It is possible that these lectins are present in the pulp of their respective fruit, complexed with starch.