Glycosidases of Molluscs

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Abstract
An α-l-fucosidase has been purified approximately 300-fold from the liver (hepatopancreas) of the marine mollusc Chamelea gallina L. (=Venus gallina L.). During the different steps of the purification procedure it was difficult to remove the contaminant N-acetylglucosaminidase activity; but, after electrofocusing, a final preprration free of this and other glycosidades present in the crude extract was obtained. The purified enzyme has a broad specificity; it hydrolyzes p-nitrophenyl α-l-fucoside and natural substrates such as oligosaccharides containing fucosidic residues with α 1–2, α 1–3 and α 1–4 linkages; also it hydrolyzes fucose-containing glycopeptides, such as thyroglobulin glycopeptide, and glycoproteins as porcine submaxillary mucin (previously rendered free of sialic acid). The enzyme has a pH optimum of 5.2 ± 0.2, with a Km of 7 × 10−5 M using p-nitrophenyl l-fucoside as substrate. It is inhibited by Hg2+ and some sugars, and activated by CN−, Zn2+, Ca2+ and EDTA. It shows two peaks by isoelectric focusing (at 6.3 and 6.6). The molecular weight of the α-l-fucosidase by gel filtration was over 200000.