Insights into ligand binding to a glutathione S-transferase from mango: Structure, thermodynamics and kinetics

We studied a mango glutathione S-transferase (GST) (Mangifera indica) bound to glutathione (GSH) and S-hexyl glutathione (GSX). This GST Tau class (MiGSTU) had a molecular mass of 25.5 kDa. MiGSTU Michaelis-Menten kinetic constants were determined for their substrates obtaining a Km, V-max and k(cat) for CDNB of 0.792 mM, 80.58 mM min (-1) and 68.49 s(-1) respectively and 0.693 mM, 105.32 mM min -1 and 89.57 s(-1), for reduced GSH respectively. MiGSTU had a micromolar affinity towards GSH (5.2 mu M) or GSX (7.8 mu M). The crystal structure of the MiGSTU in apo or bound to GSH or GSX generated a model that explains the thermodynamic signatures of binding and showed the importance of enthalpic-entropic compensation in ligand binding to Tau-class GST enzymes. (C) 2017 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.