Study on Purification and Characterization of Polyphenol Oxidase from Acetes chinensis

Acetes chinensis (belonging to the Decapoda Sergestidae genus) is widely distributed in East Asian waters and is extremely widespread and present in the shallow coastal areas of China. Polyphenol oxidase (PPO), which was extracted from Acetes chinensis, was purified in a four-step procedure involving phosphate-buffered saline treatment, ammonium sulphate precipitation, DEAE-Cellulose chromatography, and Phenyl-Sepharose HP chromatography, and then, its biochemical characterization was measured. The specific activity of the purified enzyme was increased to 643.4 U/mg, which is a 30.35 times increase in purification, and the recovery rate was 17.9%. L-dopa was used as the substrate, the enzymatic reactions catalyzed by PPO conformed to the Michaelis equation, the maximum reaction velocity was 769.23 U/mL, and the Michaelis constant K_m was 0.846 mmol/L. The optimal pH of PPO from Acetes chinensis was 7.5, and the optimal temperature was 35 °C. The metal ions experiment showed that Mn²⁺ and K⁺ could enhance the activity of PPO; that Ba²⁺ and Ca²⁺ could inhibit the activity of PPO; and that Cu²⁺ had a double effect on PPO, increasing the PPO activity at low concentrations and inhibiting the PPO activity at high concentrations. The inhibitor experiment showed that the inhibitory effects of EDTA and kojic acid were weak and that ascorbic acid and sodium pyrophosphate had good inhibitory effects. The purification and characterization of Acetes chinensis serve as guidelines for the prediction of enzyme behavior, leading to effective prevention of enzymatic browning during processing.