| Autor: |
Johnson, Karl F., Hancock, Larry W., Dawson, Glyn |
| Zdroj: |
Biochimica et Biophysica Acta. General Subjects; January 1991, Vol. 1073 Issue: 1 p120-128, 9p |
| Abstrakt: |
The lysosomal enzyme α-l-fucosidase from human skin fibroblasts is synthesized as a 53 kDa glycosylated precursor which is then proteolytically processed to a 50 kDa mature form. This was confirmed by pulse-chase labeling studies with chase times up to 72 h. In fibroblasts treated with 1-deoxymannojirimycin to prevent trimming of high mannose oligosaccharides, endoglycosidase H (endo H) treatment completely deglycosylated and reduced the size of immunoprecipitated α-fucosidase by 4–5 kDa, suggesting the presence of two oligosaccharide units. Endoglycosidase H and endo F studies on untreated α-fucosidase suggested the presence of one complex-type and one high mannose-type unit, and that the final processing from 53 to 50 kDa did not involve the removal of carbohydrate. Processing was inhibited by the thiol proteinase inhibitor Ep-459, but not by Ep-475 or leupeptin. Since Ep-459 treatment increased both α-fucosidase activity (3-fold) and the amount of immunoprecipitable α-fucosidase protein in normal human skin fibroblasts, this suggests a role for cysteine-like proteinases either directly or indirectly in lysosomal hydrolase processing and turnover. Subcellular fractionation studies revealed that the proteolytic processing of the 53 kDa precursor to the 50 kDa mature form occurred in the lysosome, or some other dense organelle. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
