Carboxypeptidase E is found in all species of vertebrates that have been examined, and is also present in many other organisms that have been studied (nematode, sea slug).  Carboxypeptidase E is not found in the fruit fly (Drosophila), and another enzyme (presumably carboxypeptidase D) fills in for carboxypeptidase E in this organism. In humans, CPE is encoded by the CPE gene.