Caractérisation, isolement et propriétés de glycosidases thyroïdiennes:β-Galactosidase, [formula omitted] et α-mannosidase

Abstract

1. 1. Sheep thyroid gland is relatively rich in glycosidases with an acid pH optimum:β-galactosidase, β- N-acetylglucosaminidase and α-mannosidase, as identified using nitrophenylglycosides. Some of their properties are reported. 2. 2. These enzymes show a subcellular distribution and a structure linked latency compatible with their main localization in lysosomes, a very heterogeneous group of particles in the thyroid tissue. 3. 3. Starting from particulate pellets, three partially purified glycosidases have been isolated using gel filtration and ion exchange chromatography: a 6.6 S β- N-acetylglucosaminidase, a 10.0 S α-mannosidase, and a 19 S β-galactosidase (more or less convertible into a 5.6 S species). 4. 4. In spite of a partly prevented instability on storage, these purified glycosidases are able to sequentially release with various yields carbohydrates from sialic acid freed thyroglobulin glycopeptides. With desialized thyroglobulin, low yields are observed, which are largely increased in the presence of thyroid proteases.