The reaction of phenolic model compounds in the laccase-mediator system (LMS) - Investigations by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS)

Matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to investigate the reaction products obtained by treatment of phenolic substances with the laccase-mediator system, consisting of the enzyme laccase and a low-molecular-weight substance, the so-called mediator. Two mediators, 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid diammonium salt (ABTS) and 1-hydroxybenzotriazole (HOBT), were employed. Polymerizing and depolymerizing properties of the LMS were investigated and assigned to specific components of the system, i. e., laccase and mediator. The polymerizing action of laccase and the ABTS cation radical on phenols was demonstrated in addition to the depolymerizing effect of the LMS. The LMS causes polymerization of phenolic substrates in the initial phase of the reaction, but then degrades the initially formed polymers. The extensive breakdown of this oligomeric and polymeric material occurs exclusively in the presence of both components, mediator and laccase. Furthermore, it is also dependent on the type of polymer formed.