Horseradish peroxidase apoprotein (apoHRP) was immobilized on a heme-modified polythiophene film, which was electro-polymerized on an indium tin oxide surface to yield immobilized and reconstituted HRP. The HRP-immobilized electrode exhibits a 6-fold enhanced electrochemical response toward hydrogen peroxide reduction relative to having the protein randomly immobilized on the polythiophene electrode. This indicates that the insertion of the heme moiety into the heme pocket of HRP leads to an increase in the electrocatalytic current.