SUBCELLULAR-DISTRIBUTION IN RAT-LIVER OF A NOVEL BROAD-SPECIFICITY (ALPHA-1-]2, ALPHA-1-]3 AND ALPHA-1-]6) MANNOSIDASE ACTIVE ON OLIGOMANNOSE GLYCANS

被引:19
作者
BONAY, P
ROTH, J
HUGHES, RC
机构
[1] NATL INST MED RES, RIDGEWAY, MILL HILL, LONDON NW7 1AA, ENGLAND
[2] UNIV ZURICH, DEPT PATHOL, DIV CELL & MOLEC PATHOL, CH-8006 ZURICH, SWITZERLAND
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1992年 / 205卷 / 01期
关键词
D O I
10.1111/j.1432-1033.1992.tb16793.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Recently, the purification to homogeneity was reported of a novel broad-specificity alpha-mannosidase from rat liver microsomal membranes [P. Bonay and R. C. Hughes (1991) Eur. J. Biochem. 197, 229-238]. The enzyme catalyzed the ordered removal of alpha-1 --> 2-, alpha-1 --> 3- and alpha-1 --> 6-linked mannose residues from Man(n)GlcNAc oligosaccharide substrates where n = 4-9. We now show by subcellular fractionation and immunocytochemistry that the novel mannosidase is present in the endoplasmic reticulum, Golgi apparatus and endosomes. Enzyme activity is enriched in a heavy Golgi membrane fraction and to lesser extent in an intermediate density Golgi membrane fraction containing GlcNAc transferase I activity and in a 'late' endosomal fraction. Low levels of enzyme activity were detectable in endoplasmic reticulum membranes and in 'early' endosomes but not in receptor-enriched and ligand-free endosomes. Assays of enzymic activity using Golgi membrane fractions in the absence and presence of Triton X-100 showed that the active site of the enzyme faces the lumen of the membrane vesicles. Antibodies directed against the purified mannosidase showed no immunological cross-reaction to known endoplasmic reticulum and Golgi mannosidases. Conversely, the purified mannosidase was not recognized by antibodies directed against endoplasmic reticulum mannosidase nor Golgi mannosidase IA.
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页码:399 / 407
页数:9
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