Developmental changes of soluble and membrane-bound aspartate aminopeptidase activities in rat brain.

G. Arechaga
B. Sánchez
F. Alba
J.D. Luna
I. Prieto
J.M. Martínez
M. Ramírez
61

Abstract

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.

Keywords:
Aging/metabolism, Aminopeptidases/metabolism, Animals, Aspartic Acid/analogs and derivatives/metabolism, Brain/embryology/enzymology, Glutamyl Aminopeptidase, Male, Membrane Proteins/metabolism, Rats, Solubility, Sprague-Dawley

Authors

G. Arechaga
B. Sánchez
F. Alba
J.D. Luna
I. Prieto
J.M. Martínez
M. Ramírez


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