Insights Into Ligand Binding to a Glutathione S-Transferase from Mango: Structure, Thermodynamics and Kinetics

Abstract 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 K m , 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 μM) or GSX (7.8 μM). 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.