title: Enzymatic detoxication, conformational selection, and the role of molten globule active sites.
abstract: The role of conformational ensembles in enzymatic reactions remains unclear. Discussion concerning "induced fit" versus "conformational selection" has, however, ignored detoxication enzymes, which exhibit catalytic promiscuity. These enzymes dominate drug metabolism and determine drug-drug interactions. The detoxication enzyme glutathione transferase A1-1 (GSTA1-1), exploits a molten globule-like active site to achieve remarkable catalytic promiscuity wherein the substrate-free conformational ensemble is broad with barrierless transitions between states. A quantitative index of catalytic promiscuity is used to compare engineered variants of GSTA1-1 and the catalytic promiscuity correlates strongly with characteristics of the thermodynamic partition function, for the substrate-free enzymes. Access to chemically disparate transition states is encoded by the substrate-free conformational ensemble. Pre-steady state catalytic data confirm an extension of the conformational selection model, wherein different substrates select different starting conformations. The kinetic liability of the conformational breadth is minimized by a smooth landscape. We propose that "local" molten globule behavior optimizes detoxication enzymes.
authors: Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610, USA.
authors: Matthew T
authors: MT
authors: Honaker
authors: Mauro
authors: M
authors: Acchione
authors: Wei
authors: W
authors: Zhang
authors: Bengt
authors: B
authors: Mannervik
authors: William M
authors: WM
authors: Atkins
mesh_terms: D055162:Biocatalysis; D002152:Calorimetry, Differential Scanning; D020134:Catalytic Domain; D005982:Glutathione Transferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008658:Inactivation, Metabolic; D007700:Kinetics; D009154:Mutation; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D011994:Recombinant Proteins; C484555:GSTA1 protein, human; D005982:Glutathione Transferase
keywords: Calorimetry; Drug Metabolism; Energy Landscape; Enzyme Catalysis; Enzyme Conformation; Glutathion; Promiscuity; Xenobiotics
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