Partial Purification and Some Properties of Polyphenoloxidases from Sago Palm

Abstract

Two polyphenoloxidases (PPO I and PPO III, EC 1.10.3.1) were extracted and partially purified from sago palm pith by hydroxylapatite chromatography, DEAE-cellulose chromatography and gel filtration. Both purified isozymes gave a single activity band on polyacrylamide gel electrophoresis. The molecular weights of both enzymes were estimated to be 40,000. They had the same pH optima of 6.5 but different temperature optima, 35°C for PPO I and 45°C for PPO III. PPO I was stable at neutral to alkaline pH and PPO III at acidic pH. PPO III was somewhat more stable than PPO I when incubated at various temperatures for 15 min. PPO I and PPO III oxidized well DL-epicatechin and d-catechin, respectively. Both enzymes were strongly inhibited by KCN, Na-diethyldithiocarbamate and NaHSO₃.