Contributions of valine-292 in the nicotinamide binding site of liver alcohol dehydrogenase and dynamics to catalysis.Rubach, J.K., Ramaswamy, S., Plapp, B.V.
(2001) Biochemistry 40: 12686-12694
- PubMed: 11601993
- PubMed Abstract:
- SUBSTITUTIONS IN THE FLEXIBLE LOOP OF HORSE LIVER ALCOHOL DEHYDROGENASE HINDER THE CONFORMATIONAL CHANGE AND UNMASK HYDROGEN TRANSFER
Ramaswamy, S.,Park, D.H.,Plapp, B.V.
(1999) Biochemistry 38: 13951
- Structure of a Triclinic Ternary Complex of Horse Liver Alcohol Dehydrogenase at 2.9 Angstroms Resolution
Eklund, H.,Samama, J.-P.,Wallen, L.,Branden, C.-I.,Akeson, A.,A Jones, T.
(1981) J.Mol.Biol. 146: 561
- Binding of Substrate in a Ternary Complex of Horse Liver Alcohol Dehydrogenase
Eklund, H.,Plapp, B.V.,Samama, J.-P.,Branden, C.-I.
(1982) J.Biol.Chem. 257: 14349
- Three-Dimensional Structure of Horse Liver Alcohol Dehydrogenase at 2.4 Angstroms Resolution
Eklund, H.,Nordstrom, B.,Zeppezauer, E.,Soderlund, G.,Ohlsson, I.,Boiwe, T.,Soderberg, B.-O.,Tapia, O.,Branden, C.-I.,Akeson, A.
(1976) J.Mol.Biol. 102: 27
The participation of Val-292 in catalysis by alcohol dehydrogenase and the involvement of dynamics were investigated. Val-292 interacts with the nicotinamide ring of the bound coenzyme and may facilitate hydride transfer. The substitution of Val-292 ...
The participation of Val-292 in catalysis by alcohol dehydrogenase and the involvement of dynamics were investigated. Val-292 interacts with the nicotinamide ring of the bound coenzyme and may facilitate hydride transfer. The substitution of Val-292 with Ser (V292S) increases the dissociation constants for the coenzymes (NAD(+) by 50-fold, NADH by 75-fold) and the turnover numbers by 3-7-fold. The V292S enzyme crystallized in the presence of NAD(+) and 2,3,4,5,6-pentafluorobenzyl alcohol has an open conformation similar to the structure of the wild-type apo-enzyme, rather than the closed conformation observed for ternary complexes with wild-type enzyme. The V292S substitution perturbs the conformational equilibrium of the enzyme and decreases the kinetic complexity, which permits study of the hydride transfer step with steady-state kinetics. Eyring plots show that the DeltaH for the oxidation (V(1)) of the protio and deuterio benzyl alcohols is 13 kcal/mol and that the kinetic isotope effect of 4.1 is essentially temperature-independent. Eyring plots for the catalytic efficiency for reduction of benzaldehyde (V(2)/K(p)) with NADH or NADD are distinctly convex, being temperature-dependent from 5 to 25 degrees C and temperature-independent from 25 to 50 degrees C; the kinetic isotope effect of 3.2 for V(2)/K(p) is essentially independent of the temperature. The temperature dependencies and isotope effects for V(1) and V(2)/K(p) are not adequately explained by semiclassical transition state theory and are better explained by hydride transfer occurring through vibrationally assisted tunneling.
Department of Biochemistry, The University of Iowa, Iowa City, Iowa 52242, USA.