Subcellular analysis of Tyr-aminopeptidase activities in the developing rat cerebellum.
The endogenous opioid system seems to play important roles in the developing cerebellum. The first opioid peptide isolated, Met-enkephalin, is expressed transiently in this brain area. In the present study, several enzyme activities capable of hydrolyzing enkephalins are measured during the first month of cerebellar development, using Tyr-beta-naphthylamyde as substrate and puromycin as inhibitor of one of the membrane-bound aminopeptidases. Puromycin-sensitive soluble and membrane-bound aminopeptidase activities decrease in the synaptosomal and mitochondrial fractions at the end of the first month of life, just when enkephalin-like immunoreactivity decreases in the cerebellum. Membrane-bound enzyme also decreases in the myelinic fraction. Synaptosomal activity increases after birth, coinciding with decreases in the activity in the microsomal fraction. Puromycin-insensitive and membrane-bound aminopeptidase shows less significant developmental changes and they occur mainly in the first week of life, coinciding with the axonal and dendrite growth. These results could suggest a possible role of these enzymes, together with the rest of the opioid system, in cerebellar development.
de Gandarias
J M
JM
Department of Physiology, Medical School, University of the Basque Country, Bilbao, Spain.
Irazusta
J
J
Gil
J
J
Gallego
M
M
Casis
O
O
Casis
L
L
D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D002531:Cerebellum / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure; D003600:Cytosol / Q000201:enzymology; D004745:Enkephalins / Q000378:metabolism*; D008297:Male; D008566:Membranes / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D011691:Puromycin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013347:Subcellular Fractions / Q000201:enzymology*; D013574:Synaptosomes / Q000201:enzymology
D004745:Enkephalins; D011691:Puromycin; D000626:Aminopeptidases; C025579:enkephalin degrading enzyme