Extracellular enzymes are major drivers of biogeochemical nutrient and carbon cycling in surface water. While photoinactivation is regarded as a major inactivation process of these enzymes, the underlying molecular changes have received little attention. Here, we determine the inactivation mechanisms of enzymes in surface waters. We track changes in activity during exposure to external stress (i.e., light and oxidants) and combine this with information on molecular modifications of the enzymes‘ structure.
In our recent study, we demonstrate how light exposure leads to a rapid loss of phosphatase, aminopeptidase and glucosidase activities of biofilm samples and model enzymes. An optimized proteomics approach allowed simultaneous observation of inactivation and molecular changes. Site-specific fingerprints of degradation kinetics have been generated and visualized in the three-dimensional proteins and intramolecular reactions could be traced within the molecule.
Currently, we demonstrate how proteomics techniques can be extended to other oxidative processes of enzymes including comprehensive suspect screening of oxidation products from discrete reactions such as with singlet oxygen.