title: Electrostatic transition state stabilization rather than reactant destabilization provides the chemical basis for efficient chorismate mutase catalysis.
abstract: For more than half a century, transition state theory has provided a useful framework for understanding the origins of enzyme catalysis. As proposed by Pauling, enzymes accelerate chemical reactions by binding transition states tighter than substrates, thereby lowering the activation energy compared with that of the corresponding uncatalyzed process. This paradigm has been challenged for chorismate mutase (CM), a well-characterized metabolic enzyme that catalyzes the rearrangement of chorismate to prephenate. Calculations have predicted the decisive factor in CM catalysis to be ground state destabilization rather than transition state stabilization. Using X-ray crystallography, we show, in contrast, that a sluggish variant of Bacillus subtilis CM, in which a cationic active-site arginine was replaced by a neutral citrulline, is a poor catalyst even though it effectively preorganizes chorismate for the reaction. A series of high-resolution molecular snapshots of the reaction coordinate, including the apo enzyme, and complexes with substrate, transition state analog and product, demonstrate that an active site, which is only complementary in shape to a reactive substrate conformer, is insufficient for effective catalysis. Instead, as with other enzymes, electrostatic stabilization of the CM transition state appears to be crucial for achieving high reaction rates.
authors.affiliation: Department of Chemistry, University of Oslo, NO-0315 Oslo, Norway; and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Burschowsky
authors.affiliation: Department of Chemistry, University of Oslo, NO-0315 Oslo, Norway; and.
authors.forename: André
authors.initials: A
authors.lastname: van Eerde
authors.affiliation: Department of Chemistry, University of Oslo, NO-0315 Oslo, Norway; and.
authors.forename: Mats
authors.initials: M
authors.lastname: Ökvist
authors.affiliation: Laboratory of Organic Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kienhöfer
authors.affiliation: Laboratory of Organic Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland ute.krengel@kjemi.uio.no kast@org.chem.ethz.ch hilvert@org.chem.ethz.ch.
authors.forename: Peter
authors.initials: P
authors.lastname: Kast
authors.affiliation: Laboratory of Organic Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland ute.krengel@kjemi.uio.no kast@org.chem.ethz.ch hilvert@org.chem.ethz.ch.
authors.forename: Donald
authors.initials: D
authors.lastname: Hilvert
authors.affiliation: Department of Chemistry, University of Oslo, NO-0315 Oslo, Norway; and ute.krengel@kjemi.uio.no kast@org.chem.ethz.ch hilvert@org.chem.ethz.ch.
authors.forename: Ute
authors.initials: U
authors.lastname: Krengel
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology*; D002384:Catalysis; D020134:Catalytic Domain; D002826:Chorismate Mutase / Q000737:chemistry*; D002827:Chorismic Acid / Q000737:chemistry; D002956:Citrulline / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D003509:Cyclohexanecarboxylic Acids / Q000737:chemistry; D053138:Cyclohexenes / Q000737:chemistry; D004583:Electrons; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D055672:Static Electricity
chemical_list: D003509:Cyclohexanecarboxylic Acids; D053138:Cyclohexenes; D008024:Ligands; D002956:Citrulline; D002826:Chorismate Mutase; D002827:Chorismic Acid; D010100:Oxygen; C005550:prephenic acid
keywords: X-ray crystal structures; catalysis; enzyme mechanism; near attack conformation; pericyclic reaction