Subcellular distribution of membrane-bound aminopeptidases in the human and rat brain.
We evaluated the subcellular distribution of four membrane-bound aminopeptidases in the human and rat brain cortex. The particulate enzymes under study--puromycin-sensitive aminopeptidase (PSA), aminopeptidase N (APN), pyroglutamyl-peptidase I (PG I) and aspartyl-aminopeptidase (Asp-AP)--were fluorometrically measured using beta-naphthylamide derivatives. Membrane-bound aminopeptidase activity was found in all the studied subcellular fractions (myelinic, synaptosomal, mitochondrial, microsomal and nuclear fractions), although not homogenously. Human PSA showed highest activity in the microsomal fraction. APN was significantly higher in the nuclear fraction of both species, while PG I showed highest activity in the synaptosomal and myelinic fractions of the human and rat brain. The present results suggest that in addition to inactivating neuropeptides at the synaptic cleft, these enzymes may participate in other physiological processes. Moreover, these peptidases may play specific roles depending on their activity levels at the different subcellular structures where they are localized.
Larrinaga
Gorka
G
Department of Nursing I, University of the Basque Country, Bilbao, Bizkaia, Spain. onblaeng@lg.ehu.es
Callado
Luis Felipe
LF
Agirregoitia
Naiara
N
Varona
Adolfo
A
Gil
Javier
J
D000626:Aminopeptidases / Q000145:classification / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D018826:CD13 Antigens / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D002540:Cerebral Cortex / Q000166:cytology* / Q000201:enzymology*; D043384:Glutamyl Aminopeptidase / Q000378:metabolism; D006801:Humans; D011180:Postmortem Changes; D011751:Pyroglutamyl-Peptidase I / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000201:enzymology
D000626:Aminopeptidases; C025579:enkephalin degrading enzyme; D018826:CD13 Antigens; D043384:Glutamyl Aminopeptidase; D011751:Pyroglutamyl-Peptidase I