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UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase functions through a general acid-base catalyst pair mechanism. 2005

Marcy Hernick, and Heather A Gennadios, and Douglas A Whittington, and Kristin M Rusche, and David W Christianson, and Carol A Fierke
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.

UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is a zinc-dependent enzyme that catalyzes the deacetylation of UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine to form UDP-3-O-(R-hydroxymyristoyl)glucosamine and acetate. The structural similarity of the active site of LpxC to metalloproteases led to the proposal that LpxC functions via a metalloprotease-like mechanism. The pH dependence of k(cat)/Km catalyzed by Escherichia coli and Aquifex aeolicus LpxC displayed a bell-shaped curve (EcLpxC yields apparent pKa values of 6.4+/-0.1 and 9.1+/-0.1), demonstrating that at least two ionizations are important for maximal activity. Metal substitution and mutagenesis experiments suggest that the basic limb of the pH profile is because of deprotonation of a zinc-coordinated group such as the zinc-water molecule, whereas the acidic limb of the pH profile is caused by protonation of either Glu78 or His265. Furthermore, the magnitude of the activity decreases and synergy observed for the active site mutants suggest that Glu78 and His265 act as a general acid-base catalyst pair. Crystal structures of LpxC complexed with cacodylate or palmitate demonstrate that both Glu78 and His265 hydrogen-bond with the same oxygen atom of the tetrahedral intermediate and the product carboxylate. These structural features suggest that LpxC catalyzes deacetylation by using Glu78 and His265 as a general acid-base pair and the zinc-bound water as a nucleophile.

UI MeSH Term Description Entries
D007477 Ions An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008956 Models, Chemical Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. Chemical Models,Chemical Model,Model, Chemical
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D009227 Myristic Acids 14-carbon saturated monocarboxylic acids. Tetradecanoic Acids,Acids, Myristic,Acids, Tetradecanoic
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D002101 Cacodylic Acid An arsenical that has been used as a dermatologic agent and as an herbicide. Cacodylate,Dimethylarsinate,Dimethylarsinic Acid,Acid, Cacodylic,Acid, Dimethylarsinic
D002384 Catalysis The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction. Catalyses
D004583 Electrons Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS. Fast Electrons,Negatrons,Positrons,Electron,Electron, Fast,Electrons, Fast,Fast Electron,Negatron,Positron

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