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

Puromycin-sensitive and insensitive aminopeptidase (aminopeptidase M) activ ities are measured in several subcellular fractions of the rat brain cortex and subcortex during the first postnatal month, Tyr-beta-naphthylamyde has been used as substrate and 20 mu M puromycin as selective inhibitor. We ha ve 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 a lso has significant age-related changes in the nuclear fraction. The develo pmental pattern is different, depending on the subcellular fraction analyze d. Significant developmental changes of puromycin-insensitive aminopeptidas e (aminopeptidase M) are only found in the myelinic and microsomal fraction s and they are less significant than those found in the puromycin-sensitive aminopeptidase. It has been suggested that these enzyme activities could b e involved in processes of cell proliferation, differentiation, and maturat ion. (C) 1999 Elsevier Science Inc.