Emerging tools for measuring and modeling the in situ activity of soil extracellular enzymes

Current soil enzyme methods measure potential enzyme activities, which are indicative of overall enzyme concentrations. However, they do not provide insight in the actual rates of enzymatically catalyzed reactions under natural in situ conditions. The objectives of this review are to (1) clarify what is being measured by current standard soil enzymology methods; (2) present an overview of the factors that control in situ activities of soil enzymes; and (3) evaluate how emerging technologies and modeling approaches could enhance our understanding of in situ extracellular enzyme activity (EEA). Genomic studies targeting functional genes coding for extracellular enzymes can identify the genetic potential of microbial communities to produce enzymes. Microbial regulation of enzyme production can be assessed with transcriptomic studies of mRNA. Emerging proteomic tools could be used assess the pool sizes, diversity, and microbial source of soil enzymes. New mass-spectrometry approaches can be used to quantify the products of enzymatic degradation. The insights gathered from these approaches will foster improved models of decomposition that explicitly include enzymes and microbial species or functional groups. A comprehensive approach to measuring in situ activity and elucidating the regulation of enzyme production and stabilization is required to advance our understanding of the biochemistry of decomposition.