Abstract
Aminopeptidase N was demonstrated in human dermal fibroblasts as an ectoenzyme. The enzyme has wide substrate specificity, with a K(m) of 0.63 mM and Vmax of 338 nmol min-1 mg-1. Addition of fetal calf serum to the culture medium increased aminopeptidase N activity up to 63% by 10% serum in a 48-h culture. Treatment of fibroblasts by dexamethasone increased ectoaminopeptidase N activity in a dose- and time-dependent manner. Maximal increase of aminopeptidase N occurred after treatment with 1 microM dexamethasone for 3 days. Actinomycin D, a blocker of RNA synthesis, and cycloheximide, an inhibitor of protein synthesis, did not alter basal aminopeptidase N activity. However, they prevented stimulation by dexamethasone. RU 38486, a glucocorticoid receptor antagonist, suppressed the dexamethasone-induced increase in aminopeptidase N activity. This study shows that human dermal fibroblasts contain ectoaminopeptidase N controlled by glucocorticoids through a receptor-mediated mechanism.