Some physicochemical and structural properties of two beta-fucosidases from Achatina balteata

Some properties of two beta-fucosidases from the digestive juice of a giant snail Achatina balteata were studied. Their amino acid composition was similar and both enzymes were shown to be rich in acidic and aromatic residues. Alanine was the single N-terminal residue in the two molecules. The enzymes appeared to be devoid of sialic acid but to contain galactose, glucose, mannose, fucose and hexosamines. The total sugar content was higher in beta-fucosidase I (21.6% w/w) than in beta-fucosidase II (12.7% w/w). Gel filtration and ultracentrifugation assays were consistent with an apparent molecular weight higher than 300 000 for beta-fucosidase I and of about 110 000 for beta-fucosidase II. On SDS polyacrylamide gel electrophoresis, beta-fucosidase I dissociated into two subunits (mol. wt. 190 000 and 170 000), whereas beta-fucosidase II showed a single band with a mol. w. of about 110 000. On the basis of these studies, it is concluded that the two forms are not structurally related proteins.