Abstract:

Polyphenol oxidase (PPO) from loofah was extracted, and some of its kinetic properties were studied. ThePPO was purified by ammonium sulfate precipitation, dialysis, DEAE-Cellulose DE-52 ion-exchange and SephadexG-75 gel filtration. The specific activity of the purified PPO was 957.9 U/mg, which exhibited a purification fold of 28.3and an activity recovery of 18.5%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and nativepolyacrylamidegel electrophoresis (Native-PAGE) showed that the enzyme was homogeneous as a monomeric protein. Itsmolecular weight was estimated to be 67.8 kD and it had no isozymes. The kinetic properties of the enzyme showed thatthe optimal pH and temperature were pH 6.0 and 30 ℃, respectively. The Km and Vmax towards the substrate L-dopa were1.32 mmol/L and 0.22 OD475 nm/min, respectively.

Key words: loofah, polyphenol oxidase (PPO), purification, enzymatic properties