Differential enzymatic degradation of thiazole pollutants by two different peroxidases - A comparative study

Enzyme based degradation of organic pollutants, including emerging pollutants, is a promising remediation approach due to the promiscuous nature of the technique and the wide range of available enzymes. However, it is generously assumed that all peroxidase enzymes behave similarly and may produce similar degradation products. In the present study, we have carried out detailed degradation studies on a model thiazole compound (Thioflavin T) using two of the most commonly used peroxidases - Soybean peroxidase (SBP) and Chloroperoxidase (CPO). In addition, these two peroxidases were also used to degrade a recalcitrant water pollutant, 2-mercaptobenzothiazole. Our studies show that these two enzymes have remarkably different optimum conditions for the decolorization of Thioflavin T. For example, SBP required a redox mediator for the decolorization of Thioflavin T, whereas CPO had no such requirement. Furthermore, SBP and CPO had very different thermal stabilities, with SBP showing full activity up until 80 °C, which was very different than CPO, which was almost completely inactive at 60 °C. HPLC analyses confirmed that both SBP and CPO transformed Thioflavin T into different compounds, which was further confirmed by LC-MS-MS studies. Degradation studies with 2-mercaptobenzothiazole also showed that SBP was much more efficient in degrading the pollutant and produced numerous breakdown products, whereas CPO was not as effective and generated only 2 intermediates. Our results show that related peroxidases may behave very differently and points to the need for detailed mechanistic studies to confirm the structures of the degradation intermediates produced during enzymatic remediation of emerging pollutants and other organic compounds.