Demonstration of extracellular chymotrypsin-like activity from various Legionella species.

Concentrated extracellular supernatants from Legionella pneumophila, L. bozemanii, L. dumoffi, L. gormanii, but not L. micdadei, exhibited a strong chymotrypsin-like activity upon synthetic chromogenic tri- and tetrapeptides. Bacterial cell sonic extracts showed low protease activities, different from those of the extracellular concentrates. Extracellular concentrates were also tested in the API ZYM system, where weak protease activity only was recorded. Protease inhibitors decreased the activity of the extracellular Legionella proteases upon the chromogenic peptides.