Department Environmental Chemistry

Extracellular Enzymes

Various organisms including bacteria and algae produce extracellular enzymes, which makes these molecules just as ubiquitous. The dedication of organisms to devote significant energy for the production of extracellular macromolecules has fascinated environmental chemists and microbiologists for decades. Extracellular enzymes are also referred to as “master recyclers” as they turn over vast amounts of organic matter in surface waters. Their role as such critically depends on how long they remain active outside the cell. However, we lack a comprehensive understanding of the stability of extracellular enzymes in the environment.

Ongoing projects:
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.

Title: Proteomics Workflow; Source: E. Janssen and Chr. Egli

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.

Publications

Egli, C. M.; Janssen, E. M. L. (2018) A proteomics approach to trace site-specific damage in aquatic extracellular enzymes during photoinactivation, Environmental Science and Technology, 52(14), 7671-7679, doi:10.1021/acs.est.7b06439, Institutional Repository

More publications

Elisabeth M.-L. Janssen and Kristopher McNeill (2015) Environmental photooxidation of extracellular phosphatase and the effects of dissolved organic matter. Environmental Science and Technology, 49 (2), pp. 889-896. DOI: 10.1021/es504211x.