Protein-carbohydrate interaction : On the mode of binding of aromatic moieties to concanavalin A, the phytohemagglutinin of the jack bean

Abstract

A number of meta-alkylphenyl [beta]--glucopyranosides were synthesized and their ability to inhibit the concanavalin A-polysaccharide system was examined. The binding constants of these compounds as well as other substituted phenyl [amalgamation or coproduct]--glucopyranosides were related to the hydrophobic ([pi]) and electronic ([sigma]) nature of the substituents utilizing the equations devised by Hansch S and Hammett[paragraph sign] respectively.Regression analysis of these relationships revealed that: (1) no linear correlation between the binding constants and the electronic properties of the aromatic substituents was evident; (2) the molecular volume of mono-ortho-substituents does not significantly effect the binding of aromatic [beta]--glucopyranosides to concanavalin A; and (3) the hydrophobic nature ([pi]) of ortho- and meta- but not para-substituents is closely associated with the binding of aryl [beta]--glucosides to concanavalin A.It is proposed that apolar binding involving hydrophobic interactions associated with ortho and meta but not with the para positions of the aromatic nucleus are the predominant forces involved in the binding of the phenyl moiety of phenyl [beta]--glucosides to concanavalin A.