Proteolytic activity assay based on enhanced peroxidase effect of hydrolyzed cytochrome c

A method using cytochrome c as the substrate of proteinases trypsin, chymotrypsin and subtilisin based on peroxidase effect of the formed haem octapeptide, which is much higher than that of cytochrome c, is described. The octapeptide is degraded by excess hydrogen peroxide and the competition between oxidation of guaiacol catalyzed by the octapeptide and octapeptide degradation leads under experimental conditions to rapid production of a stable colour. Absorption at 476 nm is proportional to proteolytic activity. The method was standardized using the Anson test for proteolytic activity with haemoglobin as a substrate.