Age-related alteration of renal brush border leucine aminopeptidase in rat kidney cortex.

Renal brush border enzyme activities were significantly decreased with age. The decrease was observed in the homogenate and brush border fractions. Purified leucine aminopeptidase was significantly decreased in Vmax and Km value for leucyl-beta-naphthylamide in the old rats. Heat stability of leucine aminopeptidase from both old and young rats showed biphasic, and the enzyme from old rats was more stable at 60 degrees C than that of the young. However, other properties such as molecular weight, antigenicity, charge, and optimum pH were not significantly different between young and old rats. From these results, it is suggested that age-related alteration of leucine aminopeptidase is due to a conformational change of enzyme molecule; the conformational change might occur at the active sites of the enzyme.