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

Publication date: Available online 17 January 2017
Source:Biochimie
Author(s): Ignacio Valenzuela-Chavira, Carmen A. Contreras-Vergara, Aldo A. Arvizu-Flores, Hugo Serrano-Posada, Alonso A. Lopez-Zavala, Karina D. García-Orozco, Javier Hernandez-Paredes, Enrique Rudiño-Piñera, Vivian Stojanoff, Rogerio R. Sotelo-Mundo, Maria A. Islas-Osuna
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, Vmax and kcat 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.



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