Thermodynamics of the reduction of NADP with 2-propanol catalyzed by an NADP-dependent alcohol dehydrogenase.
The apparent equilibrium constant of the biochemical reaction, 2-propanol+NADP(ox) = acetone+NADP(red), was determined at I = 0.25 M over a wide range of pH (5.63 to 8.02) and temperature (5 to 40 degrees C). The reaction was catalyzed by an NADP-dependent alcohol dehydrogenase. The results were used to calculate thermodynamic quantities for the chemical (ionic) reference reaction: 2-propanol+NADP(ox)(3-) = acetone+NADP(red)(4-)+H(+). The thermodynamic quantities for this reference reaction are as follows: equilibrium constant K = (5.98+/-0.46) x 10(-10); standard molar Gibbs energy change Delta(r)G(0) = (52.65+/-0.19) kJmol(-1); standard molar enthalpy change Delta(r)H(0) = (38.9+/-0.6) kJmol(-1); and standard molar entropy change Delta(r)S(0) = -(46.1+/-2.2)J K(-1)mol(-1). All of these results pertain to 25 degrees C (298.15 K) and I = 0. The results also lead, in conjunction with tabulated thermodynamic quantities, to the standard electromotive force E(0) = -0.140 V for the reduction of NADP(ox)(3-) to NADP(red)(4-).
King
M Todd
MT
Unit of Metabolic Control, Laboratory of Metabolism and Molecular Biology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 12501 Washington Avenue, Rockville, MD 20852, USA. tking@niaaa.nih.gov
D019840:2-Propanol / Q000494:pharmacology*; D000426:Alcohol Dehydrogenase / Q000737:chemistry* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D009249:NADP / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics
D009249:NADP; D000426:Alcohol Dehydrogenase; D019840:2-Propanol