[Kinetics of thermoinactivation of intracellular cholesterol oxidase].

It was shown that thermoinactivation of cholesterol oxidase in solution obeys the first order kinetics. The inactivation rate constants do not depend on concentrations of the enzyme, serum albumin and nonionic detergent Tween-80 and increase with a rise in ionic strength of the buffer solution and NaCl. Thermoinactivation is accompanied by a hypsochromic shift of the absorption maxima both in the short- and long-wave regions of the enzyme UV spectrum. It is assumed that the observed inactivation is due to conformational changes in the protein molecule which cause the loosening of its binding to the cofactor as well as the split-off of the latter. The value of activation energy for this process is 255 kJ/mol.