Purification, Biochemical Characterization, and Inhibition Studies of Polyphenol Oxidase from Tea (Camellia sinensis L.) Flowers

Tea (Camellia sinensis L.) flowers have recently gained attention due to their bioactive composition, similar to that of tea leaves. They are used in food and cosmetic applications and show potential for medicinal use. However, catechins in tea flowers are highly susceptible to oxidation by polyphenol oxidase (PPO), leading to enzymatic browning. This process alters the phenolic profile and results in losses in appearance, nutritional value, and overall product quality. In this study, PPO from tea flowers was purified using affinity chromatography with a yield of 11.31% and a 91.90-fold purification. The molecular weight was determined to be approximately 42.67 kDa by SDS–PAGE. Substrate specificity studies revealed the highest activity toward catechin. Optimum pH and temperature were determined to be 5.0 and 40 °C, respectively. Km and Vmax values for catechin were 0.42 mM and 8333.3 EU·mL−1·min−1, respectively. The enzyme showed high stability at pH 5.0–7.0 and remained active for 60 min at 30 °C and 40 °C. L-cysteine was found to be the most effective of the inhibitors studied. These findings contribute to the understanding of the enzymatic browning mechanism of tea flower PPO and provide important data for enzyme control in food, cosmetic, and medical applications.