| Summary: | Chemoenzymatic assay systems are widely used to detect toxicants in various samples, including food and environment specimens. These methods are based on the ability of various types of toxicant to specifically inhibit/activate the functions of individual enzymes or enzyme systems. The present study examines the possibility of using the proteolytic enzyme trypsin as a specific marker to detect protease inhibitors in different samples. The study shows that trypsin activity is not affected by various heavy metals, pesticides, or quinones at levels considerably greater than their maximum allowable concentrations (MACs) in water bodies. At the same time, the IC<sub>50</sub> value for the food preservative potassium sorbate (E202) is 15 mg/L, which is substantially lower than its acceptable daily intake (ADI). The quenching of trypsin fluorescence in the presence of potassium sorbate suggests that inhibition could occur due to the binding of the preservative to the enzyme in the region adjacent to the active center. The trypsin was immobilized in starch gel to ensure its stability in the enzyme inhibition based assay. Single-use reagents were prepared as dry starch disks that could be stored over long periods. Their sensitivity to copper (II) chloride, potassium sorbate, and chromium (III) chloride was similar to the sensitivity of the free trypsin.
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