Extracellular enzymes (exoenzymes) are the proximate agents in organic matter cycling, because they catalyze the degradation of polymeric organic components of plants (and microbes and animals) into small molecules that can be directly utilized by organisms. Once released extracellularly by their producers (mostly bacteria and fungi), exoenzymes will interact with various soil components, resulting in different specific activities, substrate accessibilities, and lifetimes. Measuring exoenzyme activity in highly heterogeneous matrices such as soil by enzyme assays is often complicated by substrate or product adsorption, affecting accurate determination of activity kinetics and thermodynamics parameters of exoenzymes in different forms. This greatly affects our capability to understand the biogeochemical processes mediated by exoenzymes.<br/>In this work, we use calorimetry to measure activity of representative exoenzymes in the absence and presence of montmorillonite and activated carbon, which possess varying adsorption capacities toward the enzymes and their substrates. Results show that calorimetry is a versatile and sensitive technique to identify and quantify the impacts of enzyme and substrate adsorption, and to obtain quantitative activity kinetics and thermodynamics parameters. The methodology can be an alternative option to conventional enzyme assays in measuring enzyme activity in heterogeneous matrices, and has important implications to understanding the functionality of exoenzymes in various ecosystems.

Calorimetric determination of extracellular enzyme activity: Elucidating the impacts of adsorptive surfaces

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.