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1、中国农业科学2008,41(2):540-545ScientiaAgriculturaSinica多酚氧化酶在荔枝果皮花色素苷降解中的作用12222庞学群，黄雪梅，杨晓棠，季作梁，张昭其12（华南农业大学生命科学学院，广州510642；华南农业大学园艺学院，广州510642）摘要：【目的】荔枝果皮褐变与花色素苷含量、多酚氧化酶（PPO）活性的关系极为密切，本研究的目的是探讨PPO催化花色素苷降解而引起果皮褐变的机理。【方法】利用纯化的荔枝果皮PPO、花色素苷、花色素、花色素的降解产物及固定化PPO，探讨PPO在花色素苷降解中的作用。【结果】纯化的荔枝果皮PPO虽不能催化花色
2、素苷降解，但在邻苯二酚存在下，花色素苷被PPO迅速降解，并形成褐色产物；PPO可直接催化氧化荔枝果皮花色素及其降解产物并形成褐色产物；利用固定化PPO建立了PPO-酚-花色素苷反应系统，表明花色素苷的降解不依赖于PPO，而仅依赖于PPO催化形成的醌类物质。【结论】在荔枝果皮褐变过程中，首先是PPO催化氧化酚类物质、花色素及其降解产物形成相应的醌类物质，醌类物质进一步氧化花色素苷，导致花色素苷含量降低、褪色或变色。关键词：荔枝；多酚氧化酶；花色素苷；降解RoleofPolyphenolOxidaseinAnthocyaninDegradationofLycheePericar
3、p12222PANGXue-qun,HUANGXue-mei,YANGXiao-tang,JIZuo-liang,ZHANGZhao-qi1(CollgeofLifeScience,SouthChinaAgriculturalUniversity,Guangzhou510642;2CollegeofHorticulture,SouthChinaAgriculturalUniversity,Guangzhou510642)Abstract:【Objective】Itiswellestablishedthatanthocyaninandpolyphenoloxidase(PPO
4、)areinvolvedinpericarpbrowningofharvestedlycheefruit.However,themechanismbywhichPPOcatalyzestheanthocyanindegradationandpericarpbrowninghasnotbeenwellunderstoodyet.【Method】TounderstandtheroleofPPOinanthocyanindegradation,theinvitrodegradationofanthocyaninswasanalyzedinthereactionscontainin
5、gthepurifiedanthocyanin,purifiedPPOoritsimmobilizedstyle,exogenousphenol,anthocyanidinoritsdegradedproducts.【Result】PurifiedPPOdidnotcatalyzethedegradationofpurifiedanthocyanin.However,inthepresenceofcatechol,anthocyaninwasdegradedrapidlybyPPOandthenformedtobebrownby-products.PPOdirectlyca
6、talyzedtheoxidationofanthocyanidinoritsdegradedby-product.AsequentialreactionsystemofPPO-phenol-anthocyaninwasestablishedbyapplicationoftheimmobilizedPPO.ThestudyindicatedthattheanthocyanindegradationwasindependentofPPO,butdependentofthequinonesgeneratedbyPPO.【Conclusion】Itwassuggestedthat
7、,duringthepericarpbrowningoflycheefruit,PPOfirstcatalyzestheoxidationofphenols,anthocyanidinand/oritsdegradedproducts,thenformsquinones,andfinallyquinonesoxidizeanthocyanintobrownby-products,leadingtothedecoloration,browningandreducedanthocyanincontent.Keyword
