Raman spectroscopic studies of native and pressure- or temperature-denatured invertase

A classical Raman vibrational spectroscopic study of conformational changes in Saccharomyces cerevisiae invertase after denaturation by temperature or pressure is described. Spectra were obtained from enzyme solutions and from lyophilized forms for native invertase and after pressure-or temperature-induced deactivation. For the native invertase spectra, tentative assignments of the main characteristic protein vibrations, as polypeptidic backbone, sugars, amides and amino acids vibrations are proposed. The irreversible conformational changes monitored by Raman spectroscopy for temperature-or pressure-induced deactivation were also followed. High-pressure denaturation of invertase leads to an increase in low-wavenumber scattering in solution and to a shift of amide I bands to lower wavenumbers, observed by recording spectra after lyophilization of pressure-treated samples. However, temperature denaturation does not show such modifications in the spectra, either for low-wavenumber scattering experiments in solution or for spectra recorded after lyophilization. Thus the microscopic processes involved in inactivation are different for temperature and pressure treatments and different conformational modifications are induced. (C) 1998 John Wiley & Sons, Ltd.