title: The catalytic mechanism of Drosophila alcohol dehydrogenase: evidence for a proton relay modulated by the coupled ionization of the active site Lysine/Tyrosine pair and a NAD+ ribose OH switch.
abstract: The ionization properties of the active site residues in Drosophila lebanonensis alcohol dehydrogenase (DADH) were investigated theoretically by using an approach developed to account for multiple locations of the hydrogen atoms of the titratable and polar groups. The electrostatic calculations show that (a) the protonation/deprotonation transition of the binary complex of DADH is related to the coupled ionization of Tyr151 and Lys155 in the active site and (b) the pH dependence of the proton abstraction is correlated with a reorganization of the hydrogen bond network in the active site. On this basis, a proton relay mechanism for substrate dehydrogenation is proposed in which the O2' ribose hydroxyl group from the coenzyme has a key role and acts as a switch. The proton relay chain includes the active site catalytic residues, as well as a chain of eight water molecules that connects the active site with the bulk solvent.
authors.affiliation: Department of Biosciences, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Assen
authors.initials: A
authors.lastname: Koumanov
authors.forename: Jordi
authors.initials: J
authors.lastname: Benach
authors.forename: Silvia
authors.initials: S
authors.lastname: Atrian
authors.forename: Roser
authors.initials: R
authors.lastname: Gonzàlez-Duarte
authors.forename: Andrey
authors.initials: A
authors.lastname: Karshikoff
authors.forename: Rudolf
authors.initials: R
authors.lastname: Ladenstein
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D003198:Computer Simulation; D004330:Drosophila / Q000201:enzymology*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding; D011522:Protons; D013379:Substrate Specificity; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D006878:Hydroxides; D011522:Protons; D014867:Water; D009243:NAD; D014443:Tyrosine; C031356:hydroxide ion; D000426:Alcohol Dehydrogenase; D008239:Lysine