Enhanced chemiluminescence reaction applied to the study of horseradish peroxidase stability in the course of p-iodophenol oxidation.

The enhanced chemiluminescence reaction (ECL) was applied to the study of horseradish peroxidase (HRP) inactivation during the oxidation of p-iodophenol. Enzyme inactivation was shown to be the main reason for light decay in the course of the reaction. No individual effect of luminol and p-iodophenol as enhancer on HRP activity towards 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) was detected, enzymatic activity loss was detected only in the course of the ECL reaction. HRP activity towards ABTS (a colorimetric substrate) fell in a similar manner to the decay in light emission. The reactive radical species formed during enhancer oxidation were suggested as the main inactivating agents. The similarity of changes in light intensity and enzymatic activity allows one to apply the ECL reaction for testing potential stabilizers of HRP. The loss of enzyme activity can be partially explained by non-specific interaction of radical species with protein globule. The addition of bovine serum albumin provided almost complete protection of peroxidase from inactivation. This confirms the non-specific inactivation with highly reactive endogenous intermediates through the modification of a protein globule.