中文摘要：

测定了2-羟基-4-甲氧基苯甲醛和2-羟基-4-甲氧基苯甲酸两种效应物对菜粉蝶多酚氧化酶（polyphenoloxidase，简称PPO，EC．1．14．18．1）催化L-多巴（L—DOPA）氧化活力的抑制作用。结果表明，这两种效应物对该酶的活性均有明显的抑制作用，抑制中浓度（IC50）分别为2．71和5．66mmol／L，抑制常数分别为2．82和3．35mmol／L；2-羟基-4-甲氧基苯甲醛对该酶的抑制作用显著高于2-羟基-4-甲氧基苯甲酸的；这两种抑制剂对酶的抑制作用机理完全不同，2-羟基-4-甲氧基苯甲醛对酶的作用表现为混合型抑制，而2-羟基-4-甲氧基苯甲酸对酶的作用表现为竞争性抑制。研究结果为设计以该酶为靶标的杀虫剂提供理论依据。

英文摘要：

Inhibitory effects of 2-hydroxy-4-methoxy-benza[dehyde and 2-hydroxy-4-metnoxybenzoic acid on polyphenoloxidase （PPO） from larvae of Pieris rapae （L.） were studied. The results showed that both compounds could obviously inhibit enzyme activity for oxidation of L-DOPA, and their IC50 （inhibitor concentration leading to 50% activity lost） were 2.71 and 5.66 mmol/L, respectively. Their inhibition constants were 2.82 and 3. 35 mmol/L. Inhibitory ability of 2-hydroxy- 4-methoxy-benzaldehyde was much higher than that of 2-hydroxy-4-methoxy-benzoic acid. Inhibitory mechanisms of the two compounds were very different. The inhibition of 2-hydroxy-4-methoxy-benzaldehyde was mixed type while that of 2-hydroxy-4-methoxy-benzoic acid was competitive type.