Human leukocyte elastase (HLE) is a serine protease produced by neutrophils that has been implicated in diseases such as amphysema and cystic fibrosis. An HLE inhibitor may have therapeutic value in these diseases. An active site model of HLE bound to a tripeptidic trifluoromethyl ketone (TFMK) inhibitor, 2, was created from X-ray structures of HLE and porcine pancreatic elastase. Analysis of the model indicated a preferred binding ...