Cellular localization of puromycin-sensitive aminopeptidase isozymes.

We developed monoclonal antibodies (mAbs) against two isozymes of a cytosolic puromycin-sensitive aminopeptidase (PSA-I and PSA-II) purified from chicken brain. The isozymes could be distinguished using Ouchterlony double-immunodiffusion and Western immunoblot. Their distribution in neuronal and glial cells as visualized by indirect immunofluorescence with these mAbs was found to differ: PSA-I was confined mostly to glial lysosomes; PSA-II showed fibrillar distribution in both types of nerve cells, but in disparate patterns. These results and our findings of peptide structural differences suggest that the two PSA isozymes are expressed differently in the nervous system.