Effect of heme-apoprotein interactions on the activity of horseradish and wheat germ peroxidases.

The apoenzymes of horseradish and wheat germ peroxidases were reconstituted with synthetic hemins that differ from natural heme in the substitution pattern of side chains. Both enzymes show dual peroxidase and oxygenase activity, being the latter the oxidation of porphobilinogen in the presence of oxygen and a reducing agent. The oxygenase activity was almost unaffected in both enzymes reconstituted with synthetic hemes, while peroxidase activities were inhibited to different extents. According to the pattern of activity inhibition it was concluded that there is low flexibility of both apoproteins in the regions of the acid side chain contact which could be a general features of peroxidases.