Glycoprotein reglucosylation and nucleotide sugar utilization in the secretory pathway: identification of a nucleoside diphosphatase in the endoplasmic reticulum.
UDP is generated in the lumen of the endoplasmic reticulum (ER) as a product of the UDP-glucose-dependent glycoprotein reglucosylation in the calnexin/calreticulin cycle. We describe here the identification, purification and characterization of an ER enzyme that hydrolyzes UDP to UMP. This nucleoside diphosphatase is a ubiquitously expressed, soluble 45 kDa glycoprotein devoid of transmembrane domains and KDEL-related ER localization sequences. It requires divalent cations for activity and hydrolyzes UDP, GDP and IDP but not any other nucleoside di-, mono- or triphosphates, nor thiamine pyrophosphate. By eliminating UDP, which is an inhibitory product of the UDP-Glc:glycoprotein glucosyltransferase, it is likely to promote reglucosylation reactions involved in glycoprotein folding and quality control in the ER.
Trombetta
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Department of Cell Biology, Yale Medical School, PO Box 208002, New Haven, CT 06520-8002, USA. sergio.trombetta@yale.edu
Helenius
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D017766:Acid Anhydride Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002413:Cations, Divalent / Q000494:pharmacology; D002417:Cattle; D002460:Cell Line; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D016695:Glycosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006056:Golgi Apparatus / Q000201:enzymology; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D008099:Liver / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism* / Q000494:pharmacology; D013379:Substrate Specificity
D002413:Cations, Divalent; D006023:Glycoproteins; D009711:Nucleotides; D016695:Glycosyltransferases; D017766:Acid Anhydride Hydrolases; C023837:nucleoside-diphosphatase