Purification and characterization of peroxidase from Leucaena leucocephala, a tree legume

Peroxidase was purified to homogeneity from a tree legume Leucaena leucocephala. On SDS-PAGE the purified enzyme exhibited two distinct subunits each of 66 and 58 kDa. Determination of native molecular weight of the purified peroxidase revealed a size of ∼200 kDa suggesting a heterotrimeric structure (consisting of two subunits of 66 kDa and one subunit of 58 kDa) for native peroxidase. Purified peroxidase was found to be a glycoprotein (0.09 mg carbohydrates per mg purified peroxidase protein). Purified enzyme exhibited pH optimum of 5.0 and temperature optimum of 55 °C. The Michaelis–Menten constants (Km) for guaiacol, H2O2, were found to be 2.9 and 5.6 mM, respectively. Divalent cations namely, Ca2+ and Mn2+ activated peroxidase at lower concentration (up to 50 mM) while inhibited at higher concentration. Monovalent cation namely Na+ did not inhibit peroxidase at concentration as high as 4 M. L. leucocephala peroxidase was found to be unique as it was not inhibited by azide.