Immunoelectrophoretic studies on human small intestinal brush border proteins—the longitudinal distribution of peptidases and disaccharidases

The longitudinal distribution of different brush border enzymes along the human small intestine was studied by crossed immunoelectrophoresis. The results are based on biopsies taken every 50 cm in three intestines obtained at autopsy and on peroral or peroperative biopsies from the ligament of Treitz, proximal jejunum and distal ileum from 11 patients undergoing jejunoileal bypass operation for obesity. Lactasephlorizin hydrolase (EC 3.2.1.23-62) and sucrase-isomaltase (EC 3.2.1.48-10) had their highest level in jejunum with decreasing activity towards the proximal and distal ends of the intestine, while maltase (EC 3.2.1.20) increased along the intestine and reached its highest activity in the distal ileum. A carboxypeptidase (EC 3.4.12.X) is demonstrated as an enzymatic entity of the human intestine. This enzyme had a rather flat distribution curve while microvillus aminopeptidase (EC 3.4.11.2), dipeptidyl peptidase IV (EC 3.4.14.X) and aspartate aminopeptidase (EC 3.4.11.7) all increased along the length axis and reached maximum values in distal ileum.