Purificação parcial e caracterização da enzima polifenol oxidase em manjericão ‘Genovese’

Basil (Ocimum basilicum) has several purposes as medicinal, culinary, cosmetic and has antimicrobial and antioxidant properties. However, basil stored under low temperatures may present symptoms of cold injury and darkening caused by the action of the enzyme polyphenol oxidase. The objective of this work was to evaluate the optimum conditions for polyphenol oxidase activity and possible ways of inactivating them. The extraction of polyphenol oxidase (EC 1.10.3.1, PPO) in basil leaves 'Genovese' was optimized by saturation with 60 and 80% of ammonium sulfate. The purified PPO had a higher affinity for the catechol substrate. The optimum pH and temperature values for the activity of the enzyme were 6.5 and 30 °C, respectively. The enzyme showed stability up to 120 min of evaluation, at pH 9.0 at 4 °C and at 25 °C and pH 2.5 at 25 °C. The time of 10 min was enough to inactivate 65% of the activity at 50 °C and at 60 °C there was an 80% reduction in PPO activity. The action of the enzyme was completely inhibited by ascorbic acid, L-cysteine, sodium diethyldithiocarbamate, and tropolone.