Polyphenol oxidase (PPO) activity in leaves of Rhizophora

Abstract

Polyphenol oxidases (PPO) are enzymes that catalyze the oxidation of certain phenolic substrates to quinones in the presence of molecular oxygen. This study was carried to determine the polyphenoloxidase (PPO) activity in different position of leaves in R. apiculata and R. mucronata. The PPO activity was also measured when subjected to different pH of extraction buffer (pH 5.8, 6.4 and 8.0) and different substrate specificity which are cathecol, pyragallol and 4-methylcathecol. R. mucronata has highest PPO activity than R. apiculata in all leaf samples. The PPO activity in R. mucronata are 992±22.9 unit/μg proteins and R. apiculata are 968 ± 12.9 unit/μg proteins in old leaves. The most suitable pH for PPO activity in R. apiculata is pH 8.0 while R. mucronata is pH 5.8. The enzyme seemed to have the highest affinity (lowest Km value) for cathecol for R. mucronata and 4-methylcathecol for R. apiculata. Hence, from the Vmax/Km values, 4- methycathecol is preferred phenolic substrate for R. apiculata and R. mucronata is cathecol. Further study is required to determine the characterization the PPO in Rhizophoraceae sp.