Soil enzimology: classical and molecular approaches

Both classical and molecular approaches in soil enzymology are discussed. The detection of genes encoding enzymes combined with measurements of the relative soil enzyme activity has given insights on the origin of the measured enzymes. It is also discussed the main findings and future research about assays, kinetics, use of enzyme activities as indicators of soil functions, and location, state and role of extracellular stabilized enzymes in soil. Most of these aspects have been debated in the extensive bibliography, which is nowadays sometime ignored, probably because published in books, which, particularly those published before 1990s, are not accessible by the electronic searches. It is still problematic to use enzyme activities as indicators of soil functions because: i) present enzyme assays determine potential and not real enzyme activities; ii) the meaning of measured enzyme activities is not known; iii) the biochemistry of the process is often neglected when the target enzyme activity is assumed be an indicator of the nutrient dynamics in soil; iv) spatio-temporal variations are not always considered in situ experiments; v) many direct and indirect effects make difficult the interpretation of the response of the enzyme activity to perturbations, changes in the soil management, changes in the plant cover of soil, etc. However, combining measurements of enzyme activity in soil with expression (transcriptomics and proteomics) of genes encoding the relative enzymes may contribute to understanding the mode and timing of microbial communities responses to the substrate availability and the persistence and the stabilization of enzymes in the soil, and detecting the loci of enzyme production.