PEP A9, a new, unstable variant in the peptidase A system.

A rare peptidase A variant, tentatively designated PEP A9, was observed in six members of a German family, indicating autosomal codominant inheritance. The electrophoretic mobility is similar to that of PEP A 3-1, but it has very low in vivo stability. There is no apparent association with a disease state. A simple and sensitive staining reagent for PEP A was found in o-phthalaldehyde.