Extracellular tyrosinase from the fungus Trichoderma reesei shows product inhibition and different inhibition mechanism from the intracellular tyrosinase from Agaricus bisporus

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• 作者：Chiara Gasparetti^a ; ^{ext-Chiara.Gasparetti@vtt.fi} ; Emilia Nordlund^a ; ^{Emilia.Nordlund@vtt.fi} ; Janne Jä ; nis^b ; ^{Janne.Janis@uef.fi} ; Johanna Buchert^a ; ^{Johanna.Buchert@vtt.fi} ; Kristiina Kruus^a ; ^{Kristiina.Kruus@vtt.fi}
• 关键词：Tyrosinase ; Trichoderma reesei ; Agaricus bisporus ; End product inhibition ; Dopachrome ; Ki
• 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
• 出版年：2012
• 期刊代码：161_15709639
• 类别：bio
• 出版时间：April, 2012
• 卷：1824
• 期：4
• 页码：598-607
• 文件大小：1064 K

摘要

Tyrosinase (EC 1.14.18.1) is a widely distributed type 3 copper enzyme participating in essential biological functions. Tyrosinases are potential biotools as biosensors or protein crosslinkers. Understanding the reaction mechanism of tyrosinases is fundamental for developing tyrosinase-based applications. The reaction mechanisms of tyrosinases from Trichoderma reesei (TrT) and Agaricus bisporus (AbT) were analyzed using three diphenolic substrates: caffeic acid, L-DOPA (3,4-dihydroxy-l-phenylalanine), and catechol. With caffeic acid the oxidation rates of TrT and AbT were comparable; whereas with L-DOPA or catechol a fast decrease in the oxidation rates was observed in the TrT-catalyzed reactions only, suggesting end product inhibition of TrT. Dopachrome was the only reaction end product formed by TrT- or AbT-catalyzed oxidation of L-DOPA. We produced dopachrome by AbT-catalyzed oxidation of L-DOPA and analyzed the TrT end product (i.e. dopachrome) inhibition by oxygen consumption measurement. In the presence of 1.5 mM dopachrome the oxygen consumption rate of TrT on 8 mM L-DOPA was halved. The type of inhibition of potential inhibitors for TrT was studied using p-coumaric acid (monophenol) and caffeic acid (diphenol) as substrates. The strongest inhibitors were potassium cyanide for the TrT-monophenolase activity, and kojic acid for the TrT-diphenolase activity. The lag period related to the TrT-catalyzed oxidation of monophenol was prolonged by kojic acid, sodium azide and arbutin; contrary it was reduced by potassium cyanide. Furthermore, sodium azide slowed down the initial oxidation rate of TrT- and AbT-catalyzed oxidation of L-DOPA or catechol, but it also formed adducts with the reaction end products, i.e., dopachrome and o-benzoquinone.