Evidence of degradation process of sucrase-isomaltase in jejunum of adult rats

• Published in: Biochemical journal Vol. 229; no. 3; pp. 751 - 758
• Main Authors: Goda, T, Koldovský, O
• Format: Journal Article
• Language: English
• Published: England 01-08-1985
• Subjects: Animals; Antigens - analysis; Biliary Tract - metabolism; Binding Sites; Immunoelectrophoresis, Two-Dimensional; Jejunum - enzymology; Jejunum - immunology; Multienzyme Complexes - metabolism; Oligo-1,6-Glucosidase - metabolism; Pancreas - metabolism; Rats; Rats, Inbred Strains; Sucrase - metabolism; Sucrase-Isomaltase Complex - immunology; Sucrase-Isomaltase Complex - metabolism; Trypsin - metabolism
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2290751

To evaluate degradation processes of sucrase-isomaltase in adult rat jejunum, we determined enzymic activity of sucrase and isomaltase and compared it with the amount of immunoreactive sucrase-isomaltase. In rats fed or starved for 18h, killed at 10:00 h or 22:00 h, sucrase activity (expressed on the basis of total protein or of immunoreactive sucrase-isomaltase) was significantly (P less than 0.02) lower in the lower jejunum than in the upper jejunum; isomaltase activity was similar in both segments. Crossed immunoelectrophoresis demonstrated the existence of a second sucrase-isomaltase antigen reacting with anti-(sucrase-isomaltase) serum. This antigen was present in larger amounts in the lower jejunum than in the upper jejunum, exhibited immunological partial identity with the intact sucrase-isomaltase, and had isomaltase activity but no sucrase activity. Results suggest that this antigen is a degradation product of sucrase-isomaltase in which the sucrase active site has been broken down. To examine the role of pancreatic enzymes in degradation of sucrase-isomaltase, common pancreatico-biliary ducts were ligated. Within 18 h after the operation, the difference of sucrase activity between the upper and the lower jejunum disappeared and the amount of the second sucrase-isomaltase antigen markedly decreased in the lower jejunum. Our results indicate that, during the degradation of intestinal sucrase-isomaltase by the pancreatic proteinases, degradation of the sucrase active site precedes that of the isomaltase active site.