Processing of iduronate 2-sulphatase in human fibroblasts.
Iduronate 2-sulphatase (IDS) is a lysosomal enzyme involved in degradation of dermatan sulphate and heparan sulphate. Antigenic material was obtained either by purification of placental IDS (A and B forms) or by expression of three different fusion peptides in Escherichia coli allowing the production of five specific antibodies. Pulse-chase-labelling experiments in over-expressing fibroblasts showed poor IDS processing but large amounts of precursors were secreted into the medium. The endocytosis of the 35S- or 33P-labelled precursors by deleted fibroblasts together with glycosylation studies and proteolysis inhibition by leupeptin allowed better elucidation of IDS maturation. The initial 73-78 kDa form is converted into a phosphorylated 90 kDa precursor after modification of its oligosaccharide chains in the Golgi apparatus. This precursor is processed by proteolytic cleavage through various intermediates to a major 55 kDa intermediate, with the release of an 18 kDa polypeptide. Further proteolytic cleavage by a thiol protease gives the 45 kDa mature form containing hybrid and complex-type oligosaccharide chains.
Froissart
R
R
Centre d'Etudes des Maladies Métaboliques, Hôpital Debrousse, Lyon, France.
Millat
G
G
Mathieu
M
M
Bozon
D
D
Maire
I
I
D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D016521:Electrophoresis, Gel, Pulsed-Field; D004705:Endocytosis; D005347:Fibroblasts / Q000201:enzymology; D006031:Glycosylation; D006801:Humans; D006868:Hydrolysis; D007066:Iduronate Sulfatase / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D017931:DNA Primers; D010455:Peptides; D011993:Recombinant Fusion Proteins; D007066:Iduronate Sulfatase