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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
Author(s) -
Koumanov Assen,
Benach Jordi,
Atrian Silvia,
GonzàlezDuarte Roser,
Karshikoff Andrey,
Ladenstein Rudolf
Publication year - 2003
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.10354
Subject(s) - active site , chemistry , deprotonation , protonation , stereochemistry , hydrogen bond , cofactor , ribose , proton , photochemistry , catalysis , molecule , enzyme , biochemistry , physics , organic chemistry , ion , quantum mechanics
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. Proteins 2003;51:289–298. © 2003 Wiley‐Liss, Inc.