ABSTRACT

Soil enzyme activities are the driving force behind all biochemical transformations occurring in soil. Soil is a complex environment where several inorganic and organic components are simultaneously present and exert their action. ¤ese components may a¦ect the synthesis, persistence, stabilization, regulation, and catalytic behavior of enzymatic proteins, present at any moment in the soil environment. In soil, enzyme activities outside the cells exhibit altered catalytic, kinetic, and stability properties. For these peculiar features and properties, they can be regarded as “naturally immobilized enzymes.” Several studies have demonstrated that clay minerals, organic matter (OM), and organo-mineral complexes are involved in the interaction with enzyme activities and the immobilization of enzymes in soil. Two methodological approaches have been used for understanding the relationships between immobilized soil enzymes and their clay, humic, or humic-clay supports (Gianfreda and Bollag, 1996). ¤e rst approach is based on the isolation, puri-cation, and characterization of active enzymatic fractions from soils. In the second approach, synthetic model systems, in which enzymes are articially immobilized by their attachment to soil components, have been used for studying the properties of soilbound enzymes.