Binding kinetics of methyl .alpha.-D-mannopyranoside to concanavalin A: temperature-jump relaxation study with 4-methylumbelliferyl .alpha.-D-mannopyranoside as a fluorescence indicator ligand

Abstract

The binding of methyl .alpha.-D-mannopyranoside and methyl .alpha.-D-glucopyranoside of concanavalin A (Con A) investigated by the temperature-jump relaxation kinetic technique using the competitive inhibitor 4-methylumbelliferyl .alpha.-D-mannopyranoside as an indicator of the binding reaction. These saccharides bind to Con A in a single bimolecular step. The binding parameters are compared to those of derivatized carbohydrates which have previously been used to study the binding of saccharides to Con A. The similarity of the association rate constants indicates that a common process is involved in the binding of all carbohydrates to Con A. The different affinities of saccharides for the lectin are primarily due to the different dissociation rate constants. A discussion of the proposed mechanism is given to clarify the fact that one of the observed relaxation times is faster than is possible with only the kinetic indicator reaction.