中文摘要：

多酚氧化酶（PPO）是生物体内黑色素合成的关键酶。研究了甜柿叶乙醇提取物、涩柿叶乙醇提取物、甜柿叶水提取物、涩柿叶水提取物对马铃薯多酚氧化酶活性的抑制作用。结果表明，上述4种柿叶提取物对马铃薯多酚氧化酶具有明显的抑制作用，使该酶活力下降50％所需的浓度（IG50）分别为0．21、0．26、0．37、0．45mg／mL。乙醇提取物较水提取物的作用效果更强，甜柿叶提取物的抑制作用比涩柿叶提取物的强，4种柿叶提取物对酶的抑制作用均为非竞争性可逆抑制，其抑制常数（KI=KIS）分别为0．18、0．23、0．34、0．45mg／mL。

英文摘要：

Polyphenol oxidase （PPO） is a key enzyme in pigment biosynthesis of organisms. The inhibitory effects on the activity of potato PPO by ethanol extract of sweet persimmon leaf, ethanol extract of astringent persimmon leaf, water extract of sweet persimmon leaf and water extract of astringent persimmon leaf were compared. The results showed that extract of persimmon leaf could obviously inhibit the activity of potato PPO. The inhibitors concentration leading to 50% （IC50） of the enzyme activity lost were 0.21, 0.26, 0. 37, 0.45 mg/mL, respectively. The inhibition strength of ethanol extract was stronger than that of water extract, and extract of sweet persimmon leaf is stronger than that of extract of astringent persimmon leaf. Kinetic analyses showed that the inhibition mechanism of all four extracts was noncompetitive inhibition, and the inhibition constants （KI=KIS） were 0.18, 0. 23, 0. 34, 0. 45 mg/mL, respectively.