Dipeptidyl aminopeptidase activities of guinea-pig brain

1. The subcellular distribution of dipeptidyl aminopeptidase activities in guinea-pig brain was investigated. Our studies show that DAP I (Gly-Arg-NH-Mec hydrolase) type activity was found to have an acidic optimum and was associated with the nuclear pellet. 2. No DAP II (Lys-Ala-NH-Mec hydrolase) type activity could be detected. Apparent hydrolysis was mainly due to aminopeptidase activity. 3. DAP III (Arg-Arg-NH-Mec hydrolase) type activity is largely cytoplasmic, but there was evidence of a membrane form associated with the synaptosomes. 4. DAP IV (Gly-Pro-NH-Mec hydrolase) type activity is present on the synaptosomal membrane, and also enriched in the microsomes. A soluble form of Gly-Pro-NH-Mec hydrolase activity is also present in the cytoplasm. Whether this activity is a DAP II or IV type activity is still yet to be determined.