A histochemical study of arylaminopeptidases in hydantoin induced hyperplastic, healthy and inflamed human gingiva

Arylaminopeptidase activity in hydantoin induced hyperplastic, inflamed and healthy human gingiva was studied using various N-L-aminoacyl-2-naphthylamines as substrates. The activity was seen to be located in the basal cell layer of the epithelium in the entire connective tissue, but it was strongest just below the epithelium in all tissues. High enzymic activity was also observed in the inflammatory cells as well as in the capillary walls of hydantoinhyperplastic and inflamed gingiva. Strong enzymic activity was obtained when N-L-alanyl-, N-L-methionyl- and N-L-leacyl-2-naphthylamine were used as substrates. Moderate activity was observed with N-L-arginyl-2-naphthylamine and N-Llysyl-2-naphthylamine in other tissues except in healthy gingiva where the enzymic activity was low or nil. To test the possible involvement of aminopeptidase B in the material the reactions were performed both in the presence and absence of 0.2 M sodium chloride, which specifically activates this enzyme. There was no observable enzymic activity in any slices when N-L-prolyl-2-naphthylamine was used as substrate.
The role of different arylaminopeptidases in connection with gingival hyperplasia caused by diphenylhydantoin and the evident absence of enzymes specific to N-L-prolyl-2-naphthylamine are discussed.