Characterization of peroxidase from Brassica oleracea gongylodes gives a lead for use of bromocresol purple as a novel substrate for peroxidase assay

The study reports the novel results of characterization of peroxidase enzyme from Brassica oleracea gongylodes known as Navilkosu in Karnataka, India. The crude extract was concentrated by salting out at 80% ammonium sulfate saturation. Localization of activity on electropherogram revealed the presence of a major band of peroxidase activity in the dialysate. Navilkosu peroxidase (NKP) showed optimal activity at pH 6-6.5 and 35-40 degrees C. The enzyme exhibited stability in the acidic range of pH and retained around 85% of activity after 1h of incubation at 50 degrees C. NKP could decolorize bromocresol purple (BCP) and bromothymol blue (BTB) in presence of H2O2. Km values for the organic substrates namely phenol, Guaiacol, Ortho phenylenediamine, 3,3', 5,5' tetramethyl benzidine, BCP and BTB were found to be significantly lower than horseradish peroxidase (HRP). Extracts of sweet potato, cabbage, radish and HRP were also found to decolorize BCP and BTB using H2O2 as the oxidising agent. Combined with its stability and high absorptivity, use of BCP as a substrate offers a novel and sensitive assay system for peroxidases.