Binding of Manno‐oligosaccharides to Concanavalin A

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Abstract
The association constants for binding of methyl α‐d‐mannopyranoside (I), mannobiose (II) and mannotriose (III) to concanavalin A were determined in the temperature range 285–313 K by a substitution titration, using 4‐methylumbelliferyl α‐d‐mannopyranoside as a carbohydrate‐specific and fluorescent indicator. All binding equilibria are simple, but establish extremely slowly with II and III. At 298.3 K, K increases moderately from I to III: (6.4 ± 0.5) × 103, (1.2 ± 0.1) × 104 and (1.10 ± 0.05) × 105 M−1. For binding of I, II and III, the –ΔH° values are constant (36 ± 2 kJ mol−1) and equal to the average value (36.1 ± 0.6 kJ mol−1) obtained for the three corresponding 4‐methylumbelliferyl α‐d‐manno‐oligosaccharides [Van Landschoot, A., Loontiens, F. G., and De Bruyne, C. K. (1978) Eur. J. Biochem. 83, 277–285]. The data are interpreted as arising from specific binding to a single mannopyranosyl residue in (α 1 → 2)‐linked manno‐oligosaccharides.