Partial purification and characterisation of polyphenol oxidase from borage (Trachystemon orientalis ) plant

In this study, the Polyphenol oxidase enzyme which was extracted from Trachystemon orientalis (Borage) was partially purified by using gel filtration column. The crude extract was used for the characterization studies of the enzyme. Whereas PPO enzyme did not show monophenolase activity, it had diphenolase and triphenolase activity. PPO enzyme that had activity toward catechol, 4-methylcatechol, cafeic acid and pyrogallol has the greatest activity toward cafeic acid. The enzyme showed different optimum pH and temperature values for different substrates. The optimum pH was at 7,5; 5,0; 5,5 for catechol and pyrogallol, 4-methyl catechol, cafeic acid, respectively. The enzyme had an optimum temperature at 10C for catechol, 5C for 4-methyl catechol, 20C for cafeic acid and 30C for pyrogallol. We detected that Trachystemon orientalis PPO was stable against tin and lead metals and sodium azide which could cause heavy inhibition effect on other PPOs. Inhibition assays with acidic, basic and neutral aminoacids showed that all tried aminoacids had inhibitory effect on enzyme and acidic aminoacids were the most effective ones. We also found that Trachystemon orientalis PPO is more stable than other herbal PPOs depending on heat inactivation and storage stability studies.