Properties of Two Molecular Forms of β‐Glucuronidase from the Mollusc Littorina littorea L.

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Abstract
The occurrence of two molecular forms, I and II, in the β‐glucuronidase of the liver (hepatopancreas) from the marine mollusc Littorina littorea L. has been demonstrated for the first time. The two forms have been purified 355‐fold and 1262‐fold, respectively. Form I and II of β‐glucuronidase behave differently on DEAE‐cellulose chromatography, polyacrylamide gel disc electrophoresis, isoelectric focusing (pH 5.5 and 4.2, respectively), optimum pH (4.4 and 3.4–4.1, respectively), thermal stability, Km (1.2 mM and 0.5 mM with p‐nitrophenyl β‐d‐glucuronide as substrates for form I and II, respectively) and V. Their molecular weight, estimated by gel filtration through Sephadex G‐200, was about 250000 for both forms. Several subunits were separated by polyacrylamide gel electrophoresis in presence of sodium dodecyl sulphate. This β‐glucuronidase is a glycoprotein, but sialic acid(s) were not detected. The enzyme was very active on synthetic substrates and also on hexasaccharides and tetrasaccharides containing glucuronic acid residues with β 1→3 linkages; it had practically no activity on certain glycosaminoglycans. Hg2+ and glucaro‐1,4‐lactone were very effective inhibitors of this enzyme; the latter by a competitive mechanism.

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