Proteolytic enzymes play important roles in many tissues of the body. We have recently begun to characterize a protease named carboxypeptidase O (CPO), which is found in epithelial cells lining the small intestine and is able to remove C-terminal glutamates from substrate proteins. When CPO was expressed in a model epithelial cell line, it was found to be present in small intracellular vesicles of unknown identity. These CPO-expressing cells exhibited faster migration and greater cell-cell adhesion than control cells. This phenotype and other work suggest a possible role for CPO in cancer mechanisms.