title: Thermodynamics of the arginine kinase reaction.
abstract: The effect of temperature, pH, free [Mg(2+)], and ionic strength on the apparent equilibrium constant of arginine kinase (EC 2.7.3.3) was determined. At equilibrium, the apparent K' was defined as [see text] where each reactant represents the sum of all the ionic and metal complex species. The K' at pH 7.0, 1.0 mM free [Mg(2+)], and 0. 25 M ionic strength was 29.91 +/- 0.59, 33.44 +/- 0.46, 35.44 +/- 0. 71, 39.64 +/- 0.74, and 45.19 +/- 0.65 (n = 8) at 40, 33, 25, 15, and 5 degrees C, respectively. The standard apparent enthalpy (DeltaH degrees') is -8.19 kJ mol(-1), and the corresponding standard apparent entropy of the reaction (DeltaS degrees') is + 2. 2 J K(-1)mol(-1) in the direction of ATP formation at pH 7.0, free [Mg(2+)] =1.0 mM, ionic strength (I) =0.25 M at 25 degrees C. We further show that the magnitude of transformed Gibbs energy (DeltaG degrees ') of -8.89 kJ mol(-1) is mostly comprised of the enthalpy of the reaction, with 7.4% coming from the entropy TDeltaS degrees' term (+0.66 kJ mol(-1)). Our results are discussed in relation to the thermodynamic properties of its evolutionary successor, creatine kinase.
authors.affiliation: Department of Physiology and Pharmacology, James Cook University, Townsville, Queensland, Australia 4811.
authors.forename: W E
authors.initials: WE
authors.lastname: Teague
authors.forename: G P
authors.initials: GP
authors.lastname: Dobson
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D001122:Arginine Kinase / Q000187:drug effects / Q000378:metabolism*; D003402:Creatine Kinase / Q000378:metabolism; D019143:Evolution, Molecular; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008956:Models, Chemical; D009943:Organophosphorus Compounds / Q000378:metabolism; D009994:Osmolar Concentration; D013696:Temperature; D013816:Thermodynamics
chemical_list: D009943:Organophosphorus Compounds; C015441:phospho-L-arginine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D001120:Arginine; D003402:Creatine Kinase; D001122:Arginine Kinase; D008274:Magnesium