Bilirubin binding to rat liver ligandins (glutathione S-transferases A and B). Relationship between bilirubin binding and transferase activity.

Abstract

Glutathione S-transferases A and B (ligandins) from rat liver were purified by GSH-affinity chromatography.The peroxidase procedure was used to determine the dissociation constants for the binding of bilirubin at pH 6.5 to the primary binding sites; KO = 0.11 and 0.13 PM for transferases A and B, respectively.The binding of bilirubin to the secondary sites, determined by fluorescence-quenching experiments, indicated dissociation constants of 5 and 8 PM for transferases A and B. The two binding sites on either transferase A or transferase B show no cooperative interactions, unlike the situation with human liver ligandin (Simons, P.