Conformational changes of creatine kinase in trifluoroethanol solutions.

The conformational changes of creatine kinase (ATP:creatine N-phosphotransferase, EC 2.7.3.2) in trifluoroethanol solutions have been followed by fluorescence emission and circular dichroism spectra. At low trifluoroethanol concentrations, less than 15%, the enzyme was completely inactivated with no observed marked conformational changes. The fluorescence emission maximum of the native enzyme was at 337 nm. With increasing trifluoroethanol concentration, the fluorescence emission maximum red-shifted in magnitude to a maximum value (355 nm) at 40% trifluoroethanol, indicating that the tryptophan residues were completely exposed. The results obtained from CD spectra show that the presence of trifluoroethanol can induce the formation of secondary structure in the native enzyme and in urea-denatured enzyme.