Immunoelectrophoretic studies on human small intestinal brush border proteins. The residual isomaltase in sucrose intolerant patients.

Small intestinal biopsies from three patients with sucrose intolerance (sucrase-isomaltase deficiency) were studied by means of immunoelectrophoresis and enzymatic assays. All patients lacked sucrase activity (less than 1 unit/g protein). One of the patients had a substantial isomaltase activity (7.8 unit/g protein). Immunoelectrophoresis revealed the presence of the isomaltase polypeptide of the sucrase-isomaltase in this patient. None of the biopsies showed any precipitate that might represent a modified inactive sucrase protein.