RAMAN-SPECTROSCOPIC STUDIES OF NATIVE AND PRESSURE-DENATURED OR TEMPERATURE-DENATURED INVERTASE

A classical Raman vibrational spectroscopic study of conformational ch anges in Saccharomyces cerevisiae invertase after denaturation by temp erature or pressure is described. Spectra were obtained from enzyme so lutions and from lyophilized forms for native invertase and after pres sure-or temperature-induced deactivation. For the native invertase spe ctra, tentative assignments of the main characteristic protein vibrati ons, as polypeptidic backbone, sugars, amides and amino acids vibratio ns are proposed. The irreversible conformational changes monitored by Raman spectroscopy for temperature-or pressure-induced deactivation we re also followed. High-pressure denaturation of invertase leads to an increase in low-wavenumber scattering in solution and to a shift of am ide I bands to lower wavenumbers, observed by recording spectra after lyophilization of pressure-treated samples. However, temperature denat uration does not show such modifications in the spectra, either for lo w-wavenumber scattering experiments in solution or for spectra recorde d after lyophilization. Thus the microscopic processes involved in ina ctivation are different for temperature and pressure treatments and di fferent conformational modifications are induced. (C) 1998 John Wiley & Sons, Ltd.