Kinetic Characterization and Thermal Properties of Two Acidic Peroxidases from White Cabbage (Brassica Oleracea L.)

Soluble and membrane-bound peroxidases (POD) were extracted from white cabbage. Optimum activity was obtained at pH 4.0 for both enzymes. The K-M and V-m values for H2O2 were found to be 0.62 mM and 6.5 M/min, respectively, for soluble POD; and 1.1 mM and 7.75 M/min, respectively, for membrane-bound POD. The K-M and V-m values for ABTS were found to be 0.92 mM and 7.4 M/min, respectively, for soluble POD; and 0.43 mM and 6.95 M/min, respectively, for membrane-bound POD. The effect of several reducing agents was studied. The effect of cyclodextrins was studied and the complexation constant between ABTS and HP--CDs was calculated (K-c=303 M-1). A thermal inactivation study showed a first-order inactivation kinetic for both enzymes and the Arrhenius plot yielded a straight line with a slope equivalent to activation energy of 153.1 kj/mol for membrane-bound POD and 49.1 kj/mol for soluble POD. Practical ApplicationsRoots of horseradish serve at present as the major source of commercially available peroxidase. However, this peroxidase has certain problems with regard stability and inactivation under certain conditions, hence the interest in finding novel plant peroxidases with greater stability and similar applicability. White cabbage peroxidase could be highly promising for biotechnological applications, taking into account, its high activity, low cost of the raw material and the easy extraction method described.