Abstract: Disclosed herein is a therapeutic method for treating a clinical disorder associated with a mutation in the carboxypeptidase E gene. In the therapeutic method of the invention, a molecule having carboxypeptidase activity is introduced into the plasma of the individual being treated. Such molecules include, for example, carboxypeptidase H, carboxypeptidase M, carboxypeptidase N, carboxypeptidase U and carboxypeptidase B. Also disclosed are methods for identifying individuals falling within the class for which the therapeutic method described above can be effective. These methods include, for example, the isolation of DNA encoding carboxypeptidase E followed by either: 1) sequence determination and comparison to wild-type; or 2) expression and comparison of activity to wild-type activity.