关键词: 芋头；酶促褐变；多酚氧化酶；分离纯化；酶学特性

Abstract: Polyphenol oxidase (PPO) from taro was obtained and purified through sequential steps of extraction, precipitation with 30%–80% saturated ammonium sulfate, dialysis, ultrafiltration, and chromatographic separation. The PPO was enzymatically characterized and the action pattern of selected inhibitors on it was explored. The results showed that electrophoretically pure PPO was obtained using DEAE-Sepharose and Superdex G-75 column chromatography, and the specific activity was 27 471.26 U/mg, which corresponded to a 6.37-fold purification. SDS-PAGE analysis of the purified PPO showed one band at approximately 24 kDa. The enzyme showed high substrate affinity for catechol. Its binding capacity to various substrates decreased as follows: catechol > resorcinol > phloroglucinol > pyrogallic acid > L-tyrosine. The optimal reaction temperature, pH and time were 30 ℃, 6.8 and 60 s, respectively. The PPO enzyme was inhibited by ascorbic acid and L-cysteine in an uncompetitive and competitive manner, respectively. This study demonstrates that controlling the temperature and pH and adding inhibitors can reduce the occurrence of enzymatic browning during taro processing effectively.

Key words: taro; enzymatic browning; polyphenol oxidase; separation and purification; enzymatic characteristics