Alactosidase assays were performed according to the manufacturer's protocol. Surface plasmon resonance assay Surface plasmon resonance assay was performed with BIACORE 2000. Synthetic peptides were immobilized on the carboxylated dextran matrix of CM5 sensor chips through the sulfhydryl group of the N-terminal Cys by thiol activation chemistry, according to the manufacturer's protocol. GST-His-REV