title: Functional regulation of sugar assimilation by N-glycan-specific interaction of pancreatic α-amylase with glycoproteins of duodenal brush border membrane.
abstract: Porcine pancreatic α-amylase (PPA) binds to N-linked glycans of glycoproteins (Matsushita, H., Takenaka, M., and Ogawa, H. (2002) J. Biol Chem., 277, 4680-4686). Immunostaining revealed that PPA is located at the brush-border membrane (BBM) of enterocytes in the duodenum and that the binding is inhibited by mannan but not galactan, indicating that PPA binds carbohydrate-specifically to BBM. The ligands for PPA in BBM were identified as glycoprotein N-glycans that are significantly involved in the assimilation of glucose, including sucrase-isomaltase (SI) and Na(+)/Glc cotransporter 1 (SGLT1). Binding of SI and SGLT1 in BBM to PPA was dose-dependent and inhibited by mannan. Using BBM vesicles, we found functional changes in PPA and its ligands in BBM due to the N-glycan-specific interaction. The starch-degrading activity of PPA and maltose-degrading activity of SI were enhanced to 240 and 175%, respectively, while Glc uptake by SGLT1 was markedly inhibited by PPA at high but physiologically possible concentrations, and the binding was attenuated by the addition of mannose-specific lectins, especially from Galanthus nivalis. Additionally, recombinant human pancreatic α-amylases expressed in yeast and purified by single-step affinity chromatography exhibited the same carbohydrate binding specificity as PPA in binding assays with sugar-biotinyl polymer probes. The results indicate that mammalian pancreatic α-amylases share a common carbohydrate binding activity and specifically bind to the intestinal BBM. Interaction with N-glycans in the BBM activated PPA and SI to produce much Glc on the one hand and to inhibit Glc absorption by enterocytes via SGLT1 in order to prevent a rapid increase in blood sugar on the other.
authors.affiliation: Graduate School of Humanities and Sciences and the Glycoscience Institute, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
authors.forename: Kimie
authors.initials: K
authors.lastname: Asanuma-Date
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hirano
authors.forename: Na
authors.initials: N
authors.lastname: Le
authors.forename: Kotone
authors.initials: K
authors.lastname: Sano
authors.forename: Nana
authors.initials: N
authors.lastname: Kawasaki
authors.forename: Noritaka
authors.initials: N
authors.lastname: Hashii
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hiruta
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Nakayama
authors.forename: Mariko
authors.initials: M
authors.lastname: Umemura
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ishikawa
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sakagami
authors.forename: Haruko
authors.initials: H
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004386:Duodenum / Q000166:cytology / Q000378:metabolism*; D020895:Enterocytes / Q000201:enzymology; D005685:Galactans / Q000378:metabolism; D054794:Glycomics / Q000379:methods; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D037102:Lectins / Q000378:metabolism; D008024:Ligands; D008351:Mannans / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism*; D009834:Oligo-1,6-Glucosidase / Q000378:metabolism; D055292:Pancreatic alpha-Amylases / Q000378:metabolism* / Q000494:pharmacology; D011134:Polysaccharides / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D051269:Sodium-Glucose Transporter 1 / Q000378:metabolism; D013213:Starch / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism; D013552:Swine
chemical_list: D001786:Blood Glucose; D005685:Galactans; D006023:Glycoproteins; D037102:Lectins; D008024:Ligands; D008351:Mannans; D011134:Polysaccharides; D011994:Recombinant Proteins; D051269:Sodium-Glucose Transporter 1; D013213:Starch; D006026:Glycoside Hydrolases; D055292:Pancreatic alpha-Amylases; D009834:Oligo-1,6-Glucosidase; D013393:Sucrase