A novel Carica papaya fruit peel peroxidase: kinetics, stability, and dye degradation

Dyes in industrial effluents constitute a major source of environmental pollution, posing a threat to human life. The use of enzymes for bioremediation is a greener, more efficient approach than conventional methods. This study reported partial purification of a novel peroxidase (POD) from Carica papaya (pawpaw) peels using a two-step approach: 80% ammonium sulfate precipitation followed by gel filtration chromatography on Sephadex G-200. The enzyme was purified up to 24-fold with 23% yield and a specific activity of 6020.9 U/mg proteins. The molecular weight of the enzyme, determined by gel filtration, was 54.82 kDa, and the pH and temperature optima were 5.5 and 40 °C, respectively. The apparent Michaelis-Menten constants (K_m) for hydrogen peroxide (H₂O₂) and o-dianisidine were 0.026 and 0.93 mM, respectively. Metal ions: Co³⁺, K⁺, Ca²⁺, Na⁺, Fe²⁺, and Mn²⁺ inhibited activity, while Cu²⁺ was an activator in a concentration-dependent manner; 20 mM Zn²⁺ activated the enzyme. The enzyme retained 98.2% of its original activity after incubation at pH 7 and 40 °C for 30 min, while 49.8% was retained after 90 min. Peroxidase decolorized malachite green (up to 88.09%), eriochrome black T, local, methyl orange, methylene blue, and geni dyes. Hence, Carica papaya fruit peel peroxidase exhibited good stability after heat treatment. Meanwhile, the pronounced dye-decolorizing ability and the sustainable source of this peroxidase make it robust and cost-effective for biotechnological applications.