Characterization of Polyphenol Oxidase from Litchi Pericarp Using (-)-Epicatechin as Substrate

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• 作者：Liang Liu ; Shaoqian Cao ; Bijun Xie ; Zhida Sun ; Xiaoyao Li ; Wenhua Miao
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2007
• 出版时间：August 22, 2007
• 年：2007
• 卷：55
• 期：17
• 页码：7140 - 7143
• 全文大小：64K
• 年卷期：v.55,no.17(August 22, 2007)
• ISSN：1520-5118

文摘

Polyphenol oxidase (PPO) from litchi (Litchi chinensis Sonn.) pericarp was characterized using(-)-epicatechin, which was the major endogenous polyphenol in litchi pericarp as a substrate. Theoptimum pH for PPO activity with (-)-epicatechin was 7.5, and the enzyme was unstable below pH4.5 and stable in the pH range of 6.0-8.0. Residual activities of PPO were 86.25, 86.31, and 80.17%after 67 days of incubation at 4 C at pH 6.0, 7.5, and 8.0, respectively. From thermostability studies,the K_i value increased with temperature and the results suggested that the enzyme was unstableabove 45 C. Moreover, the results also provided strong evidence that the denaturalization temperatureof PPO was near 70 C. The inhibition studies indicated that L-cysteine and glutathione were stronginhibitors even at low concentrations while NaF inhibited moderately. In addition, the results alsoindicated that the inhibition mechanisms of thiol groups were different from those of halide salts.