Significance of the Enzymes Associated with Soil C and N Transformation

Soil enzymes play a crucial role in soil organic matter transformation and nutrient cycling. Enzyme productions are the result of soil microbial community expression and their metabolomic requirement. Understanding the presence and activity of the enzymes of C and N cycles in soil may have important implications on ecosystem disturbances and can help to understand the role of C and N cycling in sustainable soil management and sustaining agricultural productivity. Among the biological features, soil enzymes are often used as a reliable index of changes in the soil status as affected by differentiated natural and anthropogenic factors since they are more sensitive to any changes than other soil variables. As was shown in the reviewed literature, interest in the enzyme systems responsible for C and N transformation in soil is currently still high. This chapter presents a brief overview of earlier and recent findings dealing with the most important soil enzymes involved in the soil C and N cycle, such as cellulase, β-glucosidase, urease, invertase, laccase, peroxidase, proteases, and nitrate reductase. The role of these enzymes in soil C and N transformation, as well as possible changes in enzymatic activity as influenced by differentiated factors, was also analyzed. Moreover, still existing limits related to the methodology adopted to assay soil enzyme activities have been discussed. Additionally, one subchapter is devoted to the relationship between gene abundance and enzymatic activity in soil. The contribution of transcriptomics and proteomics in soil enzymology is still poorly developed probably because there are still some methodological problems in soil proteomics. Moreover, the relationship between enzyme activity and the gene expression in soil is an important aim of research. Finally, further research needs and directions concerning the activity of soil C- and N-cycling enzymes are outlined.