The denaturation of protein under high pressure : I. The reversal from the pressure denaturation of ovalbumin and horse serum albumin

Abstract

From the measurements of the turbidities of ovalbumin and horse serum albumin (HSA) under high pressure by means of the high pressure apparatus with optical windows, the pressure denaturations and the reversals to their native states by the release of pressure were investigated. Ovalbumia solutions were turbid more or less, though the degrees depended upon the pH and the salt content, and the turbidity did not reverse at all from the denatured states to the native ones in the case of the release of pressure. And also, the ovalbumin compressed at the pressures above about 4, 000kg/cm^2 precipitated at the isoelectric point. On the other hand, the turbidity and the solubility in water of HSA depended very sensitively on the salt content. The pH 6.0 and salt-free HSA solution became more easily turbid than in the isoelectic and salt-free solution by compression, and the reversal to the native state by the release of pressure was found, but not complete. The pH 4.8 and 6.8 salt-free HSA solutions did not become turbid under high pressure. The pH 4.8 and 6.8 buffer containing HSA solution became considerably turbid under high pressure, and then completely and rapidly reversed by releasing the pressure. The HSA solution which perfectly reversed as to turbidity was equivalent to the native solution in the solubility in water at the isoelectric point, the optical rotation, the ultraviolet absorption spectra and the reactivity of sulfhydryl groups, but different in the solubility in the 10% solution of sodium sulfate and the susceptibility to proteolysis. Therefore, HSA reverses partially from the pressure denaturation by the release of pressure as well as the urea denaturation by the dialysis.