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

Abstract 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-β-naphthylamyde has been used as substrate and 20 μM 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.