Separation of enkephalin-degrading enzymes from longitudinal muscle layer of bovine small intestine. Enzyme inhibition by arphamenine A.

The enkephalin-degrading enzymes, such as aminopeptidase, dipeptidyl aminopeptidase, dipeptidyl carboxypeptidase and carboxypeptidase, were purified partially by DEAE-cellulose column chromatography, using longitudinal muscle from bovine small intestine. These enzyme were inhibited by EDTA and o-phenanthroline. Several protease inhibitors of microbial origin, and synthetic compounds, were tested for their abilities to inhibit these enkephalin-degrading enzymes. Among them, arphamenine A, a new potent inhibitor for aminopeptidase B, was shown to be a useful compound in inhibiting all of the enkephalin-degrading enzymes in small intestine.