Inhibition of Soil Enzymes

An enzyme inhibitor is an agent that reduces enzyme activity, whereas an enzyme activator is an agent that stimulates enzyme activity (Voet and Voet 1995). The effects of inhibitors and activators on enzymes are shown in Fig. 11.1. Both of these types of agents affect the parameter Km for the enzyme reaction of interest (Km is the substrate concentration at which the reaction rate is half of the maximum rate; Stryer 1995). As seen in Fig. 11.1, Km values increase in the presence of an inhibitor and decrease in the presence of an activator.

The inhibition of soil enzyme activities by heavy metals is a very complex issue, as there are many factors that affect this inhibition. These factors can be divided into four main classes: metal factors, enzyme factors, soil factors, and plant factors. Metal factors include the heavy metal element in question, the concentration of the heavy metal, the chemical form of the heavy metal, the availability of the heavy

Metal Enzyme
Fig. 11.1 The effects of inhibitors and activators on enzyme activity (Voet and Voet 1995)

metal, and indirect effects of the heavy metal. Enzyme factors include the enzyme sensitivity, the structural inhibition of the enzyme, and the major properties of the enzyme. Soil factors include pH, organic matter, and clay. Finally, plant factors include metal accumulation and plant community effects. We now take a closer look at these factors.

Growing Soilless

Growing Soilless

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