Marjasvaara Asse, Torvinen Mika, Vainiotalo Pirjo
Department of Chemistry, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland.
J Mass Spectrom. 2004 Oct;39(10):1139-46. doi: 10.1002/jms.691.
Substituted benzyl alcohol was oxidized enzymatically with a laccase-mediator system and the products were investigated as a function of time by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (nanoESI-FTICRMS). With Trametes versicolor laccase (TVL), the mediator, 2,2',6,6'-tetramethylpiperidine-N-oxyl radical (TEMPO), undergoes oxidation and forms oxoammonium ion. Oxidized TEMPO oxidizes the alcohol and is simultaneously reduced to the N-OH form. The laccase then restores TEMPO back to the normal radical form and the oxidation cycle starts again. The role of TEMPO and the structures of its oxidized and reduced forms in the enzymatic oxidation process were clarified in collision-induced dissociation experiments and gas-phase hydrogen/deuterium (H/D) exchange reactions. The amounts of enzyme and mediator were significant for product formation: with greater amounts overoxidation products, the corresponding benzoic acid and benzonitrile were formed. Smaller amounts of laccase and mediator generated benzaldehyde in high yield. The reaction pathway for benzonitrile formation is discussed and it is suggested to start from benzaldehyde and the ammonia in the ammonium acetate buffer.
用漆酶 - 介质体系对取代苄醇进行酶促氧化，并通过纳米电喷雾电离傅里叶变换离子回旋共振质谱（nanoESI-FTICRMS）研究产物随时间的变化。使用云芝漆酶（TVL）时，介质2,2',6,6'-四甲基哌啶 - N - 氧基自由基（TEMPO）会发生氧化并形成氧鎓离子。氧化后的TEMPO氧化醇，同时被还原为N - OH形式。然后漆酶将TEMPO恢复到正常自由基形式，氧化循环再次开始。在碰撞诱导解离实验和气相氢/氘（H/D）交换反应中阐明了TEMPO及其氧化态和还原态在酶促氧化过程中的作用。酶和介质的量对产物形成很重要：量越大，过氧化产物越多，相应地会形成苯甲酸和苯甲腈。少量的漆酶和介质能高产率地生成苯甲醛。讨论了苯甲腈形成的反应途径，并提出其起始于苯甲醛和醋酸铵缓冲液中的氨。
