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Processing of iduronate 2-sulphatase in human fibroblasts
R Froissart1, G Millat, M Mathieu
1Centre d'Etudes des Maladies Métaboliques, Hôpital Debrousse, Lyon, France.
The Biochemical Journal
|July 15, 1995
Summary
Iduronate 2-sulphatase (IDS) is crucial for breaking down specific glycosaminoglycans. Researchers elucidated its complex maturation pathway, from precursor to mature enzyme, in fibroblasts.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Iduronate 2-sulphatase (IDS) is a lysosomal enzyme.
- IDS plays a vital role in the degradation of dermatan sulphate and heparan sulphate.
Purpose of the Study:
- To elucidate the maturation pathway of Iduronate 2-sulphatase (IDS).
- To investigate the processing and secretion of IDS precursors.
Main Methods:
- Purification of placental IDS and expression of fusion peptides in E. coli.
- Production of specific antibodies against IDS.
- Pulse-chase labeling experiments in over-expressing and deleted fibroblasts.
- Glycosylation studies and proteolysis inhibition assays.
Main Results:
- Over-expressing fibroblasts showed poor intracellular IDS processing and significant precursor secretion.
- Endocytosis of labeled precursors by deleted fibroblasts aided in understanding maturation.
- IDS undergoes phosphorylation and modification in the Golgi apparatus, forming a 90 kDa precursor.
- Proteolytic cleavage yields intermediates, including a 55 kDa form, and finally the 45 kDa mature enzyme.
Conclusions:
- The study details the step-by-step proteolytic processing of IDS from its precursor to the mature 45 kDa form.
- Lysosomal enzyme maturation involves phosphorylation, glycosylation, and sequential proteolytic cleavages.
- Understanding IDS maturation is key for research into related lysosomal storage disorders.