Characterization of degradation process of sucrase-isomaltase in rat jejunum with monoclonal-antibody-based enzyme-linked immunosorbent assay

• Published in: Biochemical journal Vol. 250; no. 1; pp. 41 - 46
• Main Authors: Goda, T, Quaroni, A, Koldovský, O
• Format: Journal Article
• Language: English
• Published: England 15-02-1988
• Subjects: Animals; Antibodies, Monoclonal; Chromatography, Gel; Enzyme-Linked Immunosorbent Assay; Jejunum - enzymology; Male; Multienzyme Complexes - metabolism; Pancreatic Diseases - enzymology; Pancreatic Ducts; Rats; Rats, Inbred Strains; Sucrase-Isomaltase Complex - metabolism
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2500041

As shown previously, during degradation of sucrase-isomaltase in rat jejunum, degradation of the sucrase active site occurs before that of isomaltase active site [Goda & Koldovský (1985) Biochem. J. 229, 751-758]. To characterize further the process of sucrase-isomaltase degradation in jejunum, we determined the amounts of immunoreactive sucrase-isomaltase in rat jejunum by using a monoclonal-antibody-based enzyme-linked immunosorbent assay. By employing two alternative monoclonal antibodies (one reacting with the sucrase subunit and the other reacting with the isomaltase subunit), the amount of antigen-containing sucrase subunit and the amount of antigen-containing isomaltase subunit were separately quantified. In both upper and lower jejunum of rats, the amount of antigen-containing isomaltase subunit was always higher than the amount of antigen-containing sucrase subunit. This difference was attributable mainly to a degradation product of sucrase-isomaltase, which was identified as isomaltase monomer. Occlusion of pancreatic ducts for 18 h eliminated the difference between the amount of antigen-containing sucrase subunit and the amount of antigen-containing isomaltase subunit in both upper and lower jejunum. In jejunum of control animals, the molar ratio of sucrase subunit to isomaltase subunit was estimated to be 0.32-0.52, indicating that quite a large proportion of sucrase-isomaltase (48-68%) is present as degradation products (e.g. isomaltase monomer). These results support the model of degradation process of sucrase-isomaltase in brush-border membranes of rat jejunum, whereby degradation of sucrase subunit by the action of pancreatic proteinase(s) precedes degradation of isomaltase subunit.