PEROXIDASE FROM KIWANO (CUCUMIS METULIFERUS): BIOCHEMICAL CHARACTERIZATION AND PURIFICATION BY USING THREE-PHASE PARTITIONING

Abstract

Peroxidase (POD) was extracted from kiwano (Cucumis metuliferus) and purified for the first time using three-phase partitioning (TPP). The POD was purified 4.47-fold with 138.78% recovery of enzyme activity. In the sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis, the POD showed a molecular weight of approximately 38 kDa. The optimum pH and temperature were found to be in the range of 4.0-7.5 and 30 degrees C- 40 degrees C, respectively, for substrates. The maximum substrate specificity was observed using caffeic acid (K-m = 0.03 mM) as the substrate. Seven inhibitors were investigated, of which KCN was the strongest inhibitor. Tests were performed for identifying various metal ions, of which Fe2+ was the most effective inhibitor and Hg2+ was the strongest activator. All tested organic solvents inhibited the POD activity. The optimum ionic strength of POD was found in 4 mM NaCl. The POD had a high salt tolerance with an enhancement of approximately 12%-20% enzyme activity after 2 h incubation in NaCl. Enzyme storage stability led to decrease in the POD activity by 84% at room temperature after 400 h, 83% at +4 degrees C after 60 days, and 73% at -20 degrees C after 135 days. To our knowledge, the present study is the first to report the purification and characterization of the POD extracted from kiwano, which could be useful in potential applications.