Purification and Characterization of a Digestive Cysteine Proteinase from the Field Slug (Deroceras reticulatum): A Potential Target for Slug Control

Proteinase activities present in crop, digestive gland, and salivary gland extracts of the pest slug species, Deroceras reticulatum (Muller), were investigated. The digestive gland was found to be responsible for ≈80% of the total proteolytic activity against the plant protein rubisco. This activity, also detected by maximal hydrolysis of the synthetic substrate Z-Phe-Arg-pNA at pH 6.0, was activated by thiol compounds and inhibited by the cysteine-specific proteinase inhibitors E-64 and chicken egg white cystatin (azocasein as substrate). Furthermore, activity was largely unaffected by class-specific inhibitors diagnostic for aspartic acid proteinases, metalloproteinases, or serine proteinases. Similar studies demonstrated that the weak proteolytic activities in the crop and salivary glands were due to serine proteinases and metalloproteinases. Cation-exchange chromatography of digestive gland extracts showed that the activity in the digestive gland was due to a single protein of approximate Mr 40 000, w...