The protein denaturation under high pressure : horse serum albumin

Abstract

The denaturation of horse serum albumin was studied under pressure up to 10, 000kg/cm^2 and at the temperature of 10 to 70℃. The extent of the denaturation was examined by measuring the solubility, the reactivity of sulfhydryl groups, and the susceptibility to proteolysis by the bacterial proteinase. Even if the serum albumin solution was compressed at 10, 000kg/cm^2 and at pH 4.8 adjusted with acetate buffer, only a slight opalescence was observed, and no precipitation was formed. The heat coagulation of serum albumin was remarkably retarded by the pressure up to 8, 000kg/cm^2. From the experiments of oxidation of the reactive sulfhydryl groups and of the proteolysis by proteinase, the following deductions were made : 1) The temperature coefficient of pressure denaturation is positive. 2) The amount of pressure-denatured serum albumin is at most only about a half that of heat-denatured serum albumin. Further, increasing the pressure above approximately 7, 000kg/cm^2 resulted in little or no increase in the amount of denatured protein. 3) Though measurable renaturation was not found within 3 hours after releasing pressure, the renaturation at the instance of releasing pressure may be possible. These results are considerably different from those obtained already for ovalbumin. Accordingly, it may be suggested that serum albumin considerably differs in its secondary or tertiary structures from ovalbumin.