Monoclonal antibody against human enterokinase and immunohistochemical localization of the enzyme

A monoclonal antibody, hek-1, was raised against enterokinase or enteropeptidase that had previously been partially purified from human duodenal fluid. Hek-1 showed staining of two glycoprotein bands of relative molecular weights of 260,000 and 240,000 on immunoblot analysis of partially purified enterokinase and of ammonium sulfate fraction of duodenal fluid. An enzyme immunoassay for human enterokinase was developed, making use of hek-1. Sensitivity to enterokinase was 20 times higher than that of the conventional assay where BAPA was used as a substrate. The immunohistochemical study with hek-1 showed staining of the brush border membrane and some goblet cells of the duodenum and upper jejunum but no staining of the colon epithelium.