title: High-pressure effect on the equilibrium and kinetics of cyanide binding to chloroperoxidase.
abstract: The kinetics of cyanide binding to chloroperoxidase were studied using a high-pressure stopped-flow technique at 25 degrees C and pH 4.7 in a pressure range from 1 to 1000 bar. The activation volume change for the association reaction is delta V not equal to + = -2.5 +/- 0.5 ml/mol. The total reaction volume change, determined from the pressure dependence of the equilibrium constant, is delta V degrees = -17.8 +/- 1.3 ml/mol. The effect of temperature was studied at 1 bar yielding delta H not equal to + = 29 +/- 1 kJ/mol, delta S not equal to + = -58 +/- 4 J/mol per K. Equilibrium studies give delta H degrees = -41 +/- 3 kJ/mol and delta S degrees = -59 +/- 10 J/mol per K. Possible contributions to the binding process are discussed: changes in spin state, bond formation and conformation changes in the protein. An activation volume analog of the Hammond postulate is considered.
mesh_terms: D002711:Chloride Peroxidase / Q000378:metabolism*; D003486:Cyanides / Q000378:metabolism*; D007700:Kinetics; D003904:Mitosporic Fungi / Q000201:enzymology; D010544:Peroxidases / Q000378:metabolism*; D011190:Potassium Cyanide / Q000378:metabolism*; D011312:Pressure; D011485:Protein Binding
chemical_list: D003486:Cyanides; D010544:Peroxidases; D002711:Chloride Peroxidase; D011190:Potassium Cyanide