Developmental changes of soluble and membrane-bound aspartate aminopeptidase activities in rat brain.
Specific soluble and membrane-bound aspartyl-naphthylamide hydrolyzing activities were assayed in brain subcellular fractions from rat fetuses (19-20 days of gestation), and from 1-week-old and 1-, 5- and 24-month-old rats. Both enzymatic activities showed a heterogeneous distribution, with highest concentrations mainly in the microsomal fraction. Membrane-bound activity was in most cases higher than soluble activity. With the exception of soluble activity in the nuclear and microsomal fractions, significant age-related changes were observed in all fractions for both enzymatic activities. Soluble activity showed a homogeneous developmental profile in most of the fractions, with the lowest levels in 1-month-old rats and the highest in 1-week and 5-month-old animals. However, changes in the microsomal fraction did not follow the pattern displayed by the rest of the fractions. No clear developmental profile in specific membrane-bound activity was observed, each fraction exhibiting a different sequence of changes. Whereas in 24-month-old-rats there was a significant increase in activity in homogenate, nuclear and microsomal fractions, a significant decrease was observed in the synaptosomal fraction. These results may reflect the functional status of the endogenous substrates of the enzymes.
Arechaga
G
G
Departamento de Fisiología, Facultad de Medicina, Universidad del País Vasco, Leioa-Vizcaya, Spain.
Sánchez
B
B
Alba
F
F
Luna
J D
JD
Prieto
I
I
Martínez
J M
JM
Ramírez
M
M
D000375:Aging / Q000378:metabolism; D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000196:embryology / Q000201:enzymology*; D043384:Glutamyl Aminopeptidase; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
D008565:Membrane Proteins; D001224:Aspartic Acid; C044335:aspartic acid beta-naphthylamide; D000626:Aminopeptidases; D043384:Glutamyl Aminopeptidase