Temperature dependent rise in activity of horseradish peroxidase caused by non-ionic detergents and its use in enzyme-immunoassay.

Non-ionic detergents such as polyoxyethylene-octylphenol or -sorbitolester were found to increase activity of horseradish peroxidase due to delay of inactivation in the course of substrate reaction. This rise in activity was investigated using different chromogens and was highest with o-dianisidine. An increasing stability of the enzyme to higher reaction temperatures was observed when detergents were added to the substrate solution, and the action of detergents also is enhanced with increasing reaction temperature and time. Different degrees of activation were found when comparing substrate conversion with and without detergents using free peroxidase (2.7-fold) and conjugated peroxidase bound to the solid phase by antigen antibody reaction (1.8-fold). In enzyme-immunoassay, detection limit and analytical sensitivity can be doubled.