关键词: 多酚氧化酶, 酶活性中心, 必需基团, 可逆抑制, 马铃薯

Abstract: The enzyme active center essential groups of polyphenol oxidase（PPO）from potato and its inhibitory mechanism were investigated. The essential groups of PPO active center are determined that imidazole of His，guanidinium of Arg and Trp residue，disulfide bond have contribution to the stability of active centre structure but dissociative sulfhydryl group is not the essential group for PPO react activity. These are concluded by the result of using chemical modifiers such as BrAC，Hacac，NBS，DTT and pCMB react with PPO since they have relative specificity to correspond amino acid active group. Inhibit kinetics experiments show that the 50% enzyme activity inhibit concentration（IC₅₀）of ethanol and benzoic acid are 0.12 mmol/L and 0.07 mmol/L respectively，the inhibitory mechanism of ethanol and benzoic acid to PPO are competitive and noncompetitive reversible inhibition. These results show that ethanol inhibits PPO activity by combining with enzyme active center，while benzoic acid inhibits PPO activity by combining with non-enzyme active center.

Key words: polyphenol oxidase, enzyme active center, essential group, reversible inhibition, potato