Ontogeny of puromycin-sensitive and insensitive aminopeptidase activities in several subcellular fractions of the rat brain.

Puromycin-sensitive and insensitive aminopeptidase (aminopeptidase M) activities are measured in several subcellular fractions of the rat brain cortex and subcortex during the first postnatal month. Tyr-beta-naphthylamide has been used as substrate and 20 microM puromycin as selective inhibitor. We have found that puromycin-sensitive aminopeptidase activity increases twofold in the synaptosomal and mitochondrial fractions in the first 6-9 postnatal days, just during the period of axonal and dendritic growth. This enzyme also has significant age-related changes in the nuclear fraction. The developmental pattern is different, depending on the subcellular fraction analyzed. Significant developmental changes of puromycin-insensitive aminopeptidase (aminopeptidase M) are only found in the myelinic and microsomal fractions and they are less significant than those found in the puromycin-sensitive aminopeptidase. It has been suggested that these enzyme activities could be involved in processes of cell proliferation, differentiation, and maturation.