Thermal activation of peroxidase as a lipid oxidation catalyst

Abstract

Abstract Lipid oxidation catalysis with peroxidase heat treated in vitro was strongly influenced by the pH at which the treatment was carried out, particularly in the range 5.5–6.5. Below pH 5 no increase in lipid oxidation activity occurred due to masking of the heme groups. Electron microscopy studies showed differences in size and shape of the thermal aggregates produced at pH 7.2 and 4.9. Increased lipid oxidation activity of peroxidase on heat treatment at pH 6.5 was almost exclusively associated with the aggregates, which were separated by gel chromatography from nonaggregated material containing the residual enzyme activity. Heme migration during heat treatment led to relatively higher heme content of the aggregates, thus increasing the number of catalytic sites. Thermal destruction of the heme group decreased its lipid oxidation activity.