Title : Human
lysosomal alpha-glucosidase : functional characterization of the glycosylation
sites
Abstract :
- N-linked glycosylation is one of the important events in the post-translational modification of human lysosomal alpha-glucosidase
- Phosphorylation of mannose residues ensures efficient transport of the enzyme to the lysosomes via the mannose 6-phosphate receptor
- The primary structure of lysosomal alpha-glucosidase , as deduced from the cDNA sequence , indicates that there are seven potential glycosylation sites
- We have eliminated these sites individually by site-directed mutagenesis and thereby demonstrated that all seven sites are glycosylated
- The sites at Asn-882 and Asn-925 were found to be located in a C-terminal propeptide which is cleaved off during maturation
- Evidence is presented that at least two of the oligosaccharide side chains of human lysosomal alpha-glucosidase are phosphorylated
- Elimination of six of the seven sites does not disturb enzyme synthesis or function
- However, removal of the second glycosylation site at Asn-233 interferes dramatically with the formation of mature enzyme
- The mutant precursor is synthesized normally and assembles in the endoplasmic reticulum, but immunoelectron microscopy reveals a deficiency of alpha-glucosidase in the Golgi complex and in the more distal compartments of the lysosomal transport pathway
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. glycosylation, , -, -, sites
- 3. glycosylation, , -, -, sites
- 4. glycosylated, , -, all seven sites, -
- 6. alpha-glucosidase, , lysosomal alpha-glucosidase, the oligosaccharide side chains, -
- 8. glycosylation, , -, -, site
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):