Legionella extracellular protease activity on chromogenic peptides: a simplified procedure for biochemical enzyme...

Legionella strains produce extracellular proteases. One method to demonstrate these is through the activity of broth culture filtrates on para-nitroanilide (pNA)-derivatized peptides. Previously, this method has comprised a 100-times concentration of the filtrates, in order to bring the protease activity, as measured by the liberation of free pNA from hydrolysed peptides, up to easily recordable values. By introducing a diazotation step, the sensitivity of the test has been increased sufficiently to omit the time-consuming concentration procedure. Accordingly, the analysis of extracellular Legionella proteases by pNA-derivatized peptides has become rapid and straight-forward.