Polyphenol Oxidase Activities in Japanese Pear (Pyrus pyrifolia (Burm.) Nakai) Fruit at Different Development Stages

Abstract PPO was purified from immature and mature Japanese pears (Pyrus pyrifolia) fruits through the Sepharose-4B-L-tyrosine-p-aminobenzoic acid affinity column. PPOs were purified 5.21 fold and 9.77 fold from immature and mature Japanese pears, respectively. SDS-PAGE of PPOs from there was performed. Using catechol, 4-methyl catechol, and pyrogallol as substrates, the Km and Vmax values for immature Japanese pear PPO were calculated to be 7.14 mM, 1428.57 U/(mL min); 3.33 mM, 3333.33 U/(mL min); and 6.00 mM, 10 000.00 U/(mL min), respectively. Using catechol, 4-methyl catechol, and pyrogallol as substrates, the Km and Vmax values for mature Japanese pear PPO were calculated to be 1.31 mM, 163.93 U/(mL min); 3.57 mM, 357.14 U/(mL min); 2.50 mM, 5000.00 U/(mL min), respectively. Using catechol, 4-methyl catechol, and pyrogallol as substrates, the optimum pH and temperature values for immature Japanese pear PPO were determined to be 6.5, 15°C; 6.0, 40°C; and 8.0, 15°C, respectively. Using catechol, 4-methyl catechol, and pyrogallol as substrates, the optimum pH and temperature values for mature Japanese pear PPO were determined to be 9.0, 40°C; 7.0, 15°C; and 7.5, 30°C, respectively.