title: Partial characterization of intra- and extracellular forms of the glycoprotein hemopexin in liver cell culture and cell-free translation.
abstract: Primary cultures of rat hepatocytes produce extracellular and intracellular species of hemopexin. We examined the presence of high-mannose oligosaccharides and neuraminic acid residues in these species by comparing their electrophoretic mobility on SDS-PAGE before and after digestion by endoglycosidase H and neuraminidase. The predominant intracellular form was not susceptible to digestion by neuraminidase but was sensitive to endoglycosidase treatment, which digested it to a species with a molecular weight comparable to that of the sole hemopexin species produced by tunicamycin-treated hepatocytes and that produced by in vitro translation. By contrast, both the minor intracellular and the extracellular species of hemopexin were neuraminidase-, yet not endoglycosidase H-sensitive, and may be identical. It can be concluded that the intracellular precursor contains high-mannose type oligosaccharides which are processed to complex type oligosaccharides shortly before secretion of hemopexin.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism; D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002474:Cell-Free System; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005110:Extracellular Space / Q000378:metabolism*; D006466:Hemopexin / Q000032:analysis / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008358:Mannose / Q000032:analysis; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008970:Molecular Weight; D009439:Neuraminidase / Q000378:metabolism; D009844:Oligosaccharides / Q000032:analysis; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D009844:Oligosaccharides; D012333:RNA, Messenger; D014415:Tunicamycin; D006466:Hemopexin; D009439:Neuraminidase; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008358:Mannose