关于巯基和Mn^(2+)介导豆壳过氧化物酶氧化藜芦醇的研究

Study on the Thiol and Mn^(2+)-mediated Oxidation of Veratryl Alcohol by Soybean Hull Peroxidase

藜芦醇作为非酚型木素模型物具有较高的氧化还原电位,豆壳过氧化物酶(soybeanhullperoxidase,SHP,EC.1.11.1.7)通过依赖于过氧化氢的正常过氧化物酶催化循环不能氧化藜芦醇,但在还原型谷胱甘肽、Mn2+和有机酸络合剂存在下却可以通过不依赖于过氧化氢的氧化酶反应途径完成对藜芦醇的氧化,产物为藜芦醛,反应最适pH为4.2。动力学研究表明该反应遵循顺规序列反应机制;对藜芦醇的表观KM值为4.3mmol/L,对谷胱甘肽的表观KM值为4.8mmol/L。巯基还原剂二硫苏糖醇。

veratryl alcohol,as a non phenolic lignin model compound,has a high redox potential.Soybean hull peroxidase(SHP) is unable to oxidize veratryl alcohol in its normal peroxidatic circle,but has been shown to catalyze the oxidation of veratryl alcohol to veratraldehyde in the presence of reduced glutathione,Mn 2+ ,and an organic acid metal chelator such as lactate.The optimum pH of the reaction is 4.2.The kinetic profiles indicate a reaction mechanism of the compulsory order type wherein a specific substrate must react with SHP to form an activated complex that will react with a second substrate.An apparent K M for veratryl alcohol of 4.3 mmol/L at optimum glutathione concentration and an apparent K M for glutathione of 4.8 mmol/L at optimum veratryl alcohol were obtained.In addition to glutathione,dithiothreitol,mercaptoethanol and L cysteine are capable of promoting veratryl alcohol oxidation.Non thiol reductants,such as ascorbate,do not support oxidation of veratryl alcohol.