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

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 K-m and V-max 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 K-m and V-max 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 degrees C; 6.0, 40 degrees C; and 8.0, 15 degrees 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 degrees C; 7.0, 15 degrees C; and 7.5, 30 degrees C, respectively.