Hydrolase (β-Glucanase, α-Glucanase, and Protease) Activity in Ariolimax columbianus (Banana Slug) and Arion ater (Garden Slug)

Abstract

Carboxymethylcellulase (cm-cellulase), cellulase, chitinase, amylase, and protease enzymatic activity are found in the crop fluid and digestive gland of the pulmonate gastropods Ariolimax columbianus and Arion ater. The β-glucanases (cm-cellulase, cellulase and chitinase) and α-glucanase (amylase) display acidic pH-activity optima (between pH 5 and 7) on their respective substrates (cm-cellulose, microcrystalline cellulose, chitin and starch). Protease activity (upon casein) displays a pH optimum of approximately 8.3. Comparative studies show higher specific enzyme activity in Arion ater than in Ariolimax columbianus for all five hydrolases studied. Incubation of the β-glucanases for variable times at 50°C indicates significant differences in stability between Ariolimax columbianus and Arion ater for the β-glucanases (cm-cellulase, cellulase, and chitinase). Chromatography upon Sephadex G-100 reveals enzyme heterogeneity for the β-glucanases in both species, with at least three enzyme components or complexes (of differing molecular weight) for each species that can hydrolyze cm-cellulase, cellulase, and chitinase. The β-glucanases are apparently selective and specific for their respective substrates, with some cm-cellulase isozymes unable to digest native cellulose and vice versa. Preliminary evidence for the presence of cellulose-digesting prokaryotes in the crop fluid of Arion ater is presented.