Carbohydrate binding properties of banana (Musa acuminata) lectin - I. Novel recognition of internal alpha 1,3-linked glucosyl residues

Examination of lectins of banana (Musa acuminata) and the closely related p lantain (Musa spp.) by the techniques of quantitative precipitation, hapten inhibition of precipitation, and isothermal titration calorimetry showed t hat they are mannose/glucose binding proteins with a preference for the alp ha -anomeric form of these sugars. Both generate precipitin curves with bra nched chain alpha -mannans (yeast mannans) and alpha -glucans (glycogens, d extrans, and starches), but not with linear alpha -glucans containing only alpha1,4- and alpha1,6-glucosidic bonds (isolichenan and pullulan). The nov el observation was made that banana and plantain lectins recognize internal alpha1,3-linked glucosyl residues, which occur in the linear polysaccharid es elsinan and nigeran. Concanavalin A and lectins from pea and lentil, als o mannose/glucose binding lectins, did not precipitate with any of these li near alpha -glucans. This is, the authors believe, the first report of the recogniton of internal alpha1,3-glucosidic bonds by a plant lectin. It is p ossible that these lectins are present in the pulp of their respective frui t, complexed with starch.