Immunoelectrophoretic studies on human small intestinal brush border proteins--amount of lactase protein in adult-type hypolactasia.

Jejunal biopsies from 15 Greenlandic and three Danish patients with adult type hypolactasia and nine Greenlandic and 15 Danish patients with normal lactase activity were analysed quantitatively for lactase protein by crossed immunoelectrophoresis. A constant correlation between the amount of lactase activity and immunologically reactive lactase protein was demonstrated irrespective of the lactase activity level. As immunoelectrophoresis expresses the amount of enzyme protein independent of the enzymatic activity, it is concluded that the low enzymatic activity in adults with hypolactasia is caused by a low amount of lactase and not by a modified inactive enzyme.