In:
Biochemical Journal, Portland Press Ltd., Vol. 170, No. 3 ( 1978-03-15), p. 643-650
Abstract:
Adsorptive endocytosis of five different lysosomal enzymes from various human and non-human sources was susceptible to inhibition by mannose and l-fucose, methyl α-d-mannoside, α-anomeric p-nitrophenyl glycosides of mannose and l-fucose, mannose 6-phosphate and fructose 1-phosphate. A few exceptions from this general scheme were observed for particular enzymes, particularly for β-glucuronidase from human urine. The inhibition of α-N-acetylglucosaminidase endocytosis by mannose, p-nitrophenyl α-d-mannoside and mannose 6-phosphate was shown to be competitive. The loss of endocytosis after alkaline phosphatase treatment of lysosomal enzymes supports the hypothesis that the phosphorylated sugars compete with a phosphorylated carbohydrate on the enzymes for binding to the cell-surface receptors [Kaplan, Achord & Sly (1977) Proc. Natl. Acad. Sci. U.S.A.74, 2026–2030]. Endocytosis of ‘low-uptake’ forms of α-N-acetylglucosaminidase and α-mannosidase was likewise susceptible to inhibition by sugar phosphates and by alkaline phosphatase treatment, suggesting that ‘low-uptake’ forms are either contaminated with ‘high-uptake’ forms or are internalized via the same route as ‘high-uptake’ forms. The existence of an alternative route for adsorptive endocytosis of lysosomal enzymes is indicated by the unaffected adsorptive endocytosis of rat liver β-glucuronidase in the presence of phosphorylated sugars and after treatment with alkaline phosphatase.
Type of Medium:
Online Resource
ISSN:
0264-6021
Language:
English
Publisher:
Portland Press Ltd.
Publication Date:
1978
detail.hit.zdb_id:
1473095-9
SSG:
12
