Binding of the glycopeptide antibiotic teicoplanin to D-alanyl-D-alanine-agarose: the effect of micellar aggregates.

Teicoplanin, as well as the other antibiotics of the vancomycin group, was shown to bind specifically to D-alanyl-D-alanine-agarose (D-Ala-D-Ala-AGA) (A. Corti and G. Cassani, Appl. Biochem. Biotechnol. 11, 101-110 (1985)). This finding is extended, showing that the binding is as a function of concentration and physical form of the antibiotic in solution, i.e., monomers or micellar aggregates. At concentrations below the critical micelle concentration (CMC) teicoplanin binds with an affinity and a capacity similar to the other antibiotics of the same group such as vancomycin and ristocetin A. At concentrations above the CMC three times more teicoplanin is bound to D-Ala-D-Ala-AGA than the other two antibiotics. Equilibrium binding experiments carried out at different pHs with teicoplanin in the monomeric or micellar form indicate that the excess binding of teicoplanin occurs in the presence of micelles. Elaboration of binding data according to Scatchard indicates that the maximum binding capacity of the resin is increased 3.6 times when teicoplanin is in the micellar form. On the contrary, the apparent binding affinity is lower.