纤维二糖脱氢酶生成羟自由基和还原各种自由基的研究

Generation of Hydroxyl Radical and Reduction of Radicals by Cellobiose Dehydrogenase from a White rot Fungus Schizophyllum commune

利用电子顺磁共振（ＥＳＲ）技术和硫代巴比妥酸（ＴＢＡ）反应研究了纤维二糖脱氢酶（ＣＤＨ）生成·ＯＨ和还原各种自由基的能力．以纤维二糖为电子供体时，ＣＤＨ可以生成·ＯＨ．·ＯＨ生成量与ＣＤＨ、Ｆｅ３＋和Ｏ２的浓度有关．加入过氧化氢酶可使·ＯＨ的生成明显减少．ＣＤＨ可以还原自旋加合物［ＰＢＮ－ＯＨ］·、氮氧自由基和天然木素分子中的自由基．结果表明，ＣＤＨ具有生成·ＯＨ和还原各种自由基的能力．

A cellobiose dehydrogenase (CDH) was purified from the white rot fungus Schizophyllum commune .The properties of generating hydroxyl radical and reducing radicals by the enzyme were studied by ESR technology and TBA reaction.CDH could produce hydroxyl radical in the presence of cellobiose.The amount of hydroxyl radical produced was influenced by the concentrations of CDH,O 2 and Fe 3+ in the reaction solution.When the concentrations of CDH,O 2 and Fe 3+ were increased,the amount of hydroxyl radical increased.Addition of H 2O 2 to the reaction solution enhanced the amount of hydroxyl radical surprisingly.However,addition of catalase to the reaction decreased the production of hydroxyl radical by decomposing the H 2O 2.In the presence of cellobiose,CDH could reduce not only · radical and 4 maleimideo TEMPO radical,but also milled wood lignin(MWL) radical,which showed a large variety of radical substances for the enzyme.Hydroxyl radical is a very reactive species which can disrupt crystalline cellulose and lignin.Reduction of various radicals by CDH can prevent the reploymerization of phenoxy radicals formed by ligninases and therefore promote lignin degradation.Due to these properties,it is suggested that CDH may play an important role in lignocellulose degradation.