Protoporphyrin IX potentiates horseradish peroxidase-catalyzed oxidation of NADH:Involvement of enzyme-porphyrin interaction.

Protoporphyrin IX potentiates horseradish peroxidase-catalyzed hydrogen peroxide-mediated NADH oxidation, but the porphyrin cannot change the enzyme-catalyzed o-dianisidine oxidation. Spectrofluorimetric studies reveal that an interaction occurs between horseradish peroxidase and protoporphyrin IX. The interaction is predominantly hydrophobic and entropy-driven endothermic process. This interaction may influence the potentiation effect of the protoporphyrin IX on horseradish peroxidase-catalyzed NADH oxidation because the latter has a positive correlation with the extent of binding of the protein with the porphyrin.