Sucrase-alpha-dextrinase in the spontaneously diabetic BioBreed Wistar rat: altered intracellular carbohydrate processing.
Sucrase-alpha-dextrinase (S-D), a glycoprotein hydrolase in the border surface of the enterocyte, is altered in congenitally diabetic BioBreed Wistar (BB(d)) rats. Its intracellular assembly was examined in the current studies. Following pulse-chase experiments, S--D was specifically immuno-isolated from ER-Golgi and brush border membranes, and examined by SDS-PAGE and autoradiography. While synthesis and co-translational glycosylation of an immature species, P(i), in the ER proceeded normally, post-translational maturation of the N-linked carbohydrate chains was altered in the BB(d) rat. The mature species, P(m), was 10 kDa larger in BB(d) than in normal rats, and approximately 25% of its N-linked chains remained immature. The difference in mass was attributed to an appreciably larger mass of the O-linked chains of P(m) in BB(d) rats. In vivo kinetics of intracellular assembly displayed a delay in the appearance of P(m) in Golgi (Wistar, 15 min; BB(d), 30--60 min). These experiments, revealing structural alterations in congenital diabetes suggest an important role for intracellular glycosylation in the orderly assembly and processing of brush border S-D in the enterocyte.
Najjar
S M
SM
Department of Pharmacology and Therapeutics, Medical College of Ohio, Toledo, Ohio 43614, USA. snajjar@mco.edu
Broyart
J P
JP
Hampp
L T
LT
Gray
G M
GM
D000818:Animals; D050260:Carbohydrate Metabolism; D003921:Diabetes Mellitus, Experimental; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D051381:Rats; D011922:Rats, Mutant Strains; D017208:Rats, Wistar; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis* / Q000737:chemistry; D013997:Time Factors
D006026:Glycoside Hydrolases; D013394:Sucrase-Isomaltase Complex