Metal Ion Interactions with Apo‐Concanavalin A and Some Observations on Metal Ion Requirements and Sugar Binding by Bandeiraea simplicifolia I Lectin

The kinetics of interaction of Ca 2+ ions with M ConA (M = Co 2+ , Mn 2+ , Ni 2+ and Zn 2+ ) were followed by using the quenching of fluorescence of 4‐methylumbelliferyl‐α‐D‐mannopyranoside when bound to protein. The kinetic data can be interpreted in terms of a mechanism in which a species (MCaP) 1 initially formed (constant K 1 ) transforms slowly ( k 2 ) to the final form. Values of k 1 , Δ H 1 and Δ S 1 and (particularly) k 2 , Δ H 2 ≠ and Δ S 2 ≠ are very similar for all metals, but the Δ H 2 ≠ ‐values are much lower than previously reported by other investigators. The kinetics of binding of 4‐methylumbelliferyl‐α‐D‐galactopyranoside to Bandeiraea simplicifolia I lectin were studied by stopped‐flow fluorescence methods. The formation rate constant (∼ 10 5 M −1 s −1 ) is similar to that of sugars with other lectins. EDTA removes the sugar binding ability of B. simplicifolia I lectin with t 1/2 = 24 min (pH = 7.2, 25°). The addition of Ca 2+ ions to apolectin to give a final product appears controlled by a conformational change.