[Drug binding analysis of human alpha 1-acid glycoprotein using capillary electrophoresis]

Drug-plasma protein binding analysis is indispensable for drug development and clinical use. However, conventional methods for binding analyses were not suitable for small amounts of proteins because of large sample requirements. On the other hand, high-performance frontal analysis/capillary electrophoresis (HPFA/CE) consumes very small sample volumes, and is useful for ligand-binding study of small amounts of proteins. In this study, HPFA/CE was used in a drug-binding study of alpha 1-acid glycoprotein (AGP) subtypes in which plasma concentrations change dynamically to elucidate the effects of structural variation on drug binding. Binding study on desialyrated AGP revealed that (S)-enantiomer selectivity in propranolol-AGP binding was caused by sialic acid residues, while neither sialic acid nor galactose caused the enantioselectivity of verapamil binding to AGP. Biantennary glycans slightly suppressed disopyramide binding to AGP, whereas the glycans did not have any influence on propranolol and verapamil binding. Disopyramide and verapamil were selectively bound to the A variant rather than the F1S variant. The A variant showed larger enantioselective binding to disopyramide, but not to verapamil.