Representative aminopeptidases and prolyl endopeptidase from murine macrophages: Comparative activity levels in resident and elicited cells

Macrophages are considered the main effector cells of immune system. Under stimulation these cells are known to be activated by a process involving morphological, biochemical and functional changes. Since altered peptidase activities could be among the factors leading to the differentiation and activation of these cells, in the present work seven naphthylamide derivative substrates were employed to assess representative aminopeptidase and prolyl endopeptidase activities in resident and elicited macrophages of mice. Soluble basic aminopeptidase and prolyl endopeptidase and soluble and particulate neutral and prolyl dipeptidyl aminopeptidase IV activities were present at measurable levels while particulate prolyl endopeptidase and basic aminopeptidase, and particulate and soluble cystyl and pyroglutamyl aminopeptidases were not detectable. Kinetic parameters, chloride activation and the inhibitory effects of puromycin, bestatin, amastatin and diprotin A characterized differential properties of these peptidase activities. The observed increment (about 6-17-fold) of the soluble basic aminopeptidase and prolyl endopeptidase and soluble and particulate neutral and prolyl dipeptidyl aminopeptidase IV activities in elicited macrophages was particularly relevant, as these might contribute to an increased ability of this cell to inactivate several susceptible substrates known to be inflammatory and/or immunological mediators.