title: Human placental ATP diphosphohydrolase is a highly N-glycosylated plasma membrane enzyme.
abstract: Human placental ATP diphosphohydrolase (ATP-DPH), has been previously characterized as an azide-sensitive, Ca(2+)- or Mg(2+)-dependent triphospho- and diphosphonucleosidase which migrates as an 82 kDa protein band on SDS-PAGE (Christoforidis, S. et al. (1995) Eur. J. Biochem. 234, 66-74). In this paper we have studied the subcellular localization of placental ATP-DPH by differential centrifugation and flotation experiments. Using specific enzymatic markers it was found that ATP-DPH is localized on plasma membrane. ATP-DPH was found to be a highly N-glycosylated protein which is a common post-translational modification of plasma membrane proteins. Extensive incubation of the native pure enzyme with N-glycosidase F resulted in the elimination of the 82 kDa form and the concurrent formation of a deglycosylated product of 57.5 kDa and four other intermediate products, indicating the presence of at least five N-glycosylation sites within the ATP-DPH molecule. The partially deglycosylated sample retained its activity in solution and in native gel electrophoresis and activity staining.
authors.affiliation: Laboratory of Biological Chemistry, University of Ioannina Medical School, Greece.
authors.forename: S
authors.initials: S
authors.lastname: Christoforidis
authors.forename: T
authors.initials: T
authors.lastname: Papamarcaki
authors.forename: O
authors.initials: O
authors.lastname: Tsolas
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D001081:Apyrase / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy
chemical_list: D006026:Glycoside Hydrolases; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D001081:Apyrase