Similarities between human and rat leukocyte elastase and cathepsin G.

Rat is a likely test animal for determining the efficacy of proteinase inhibitor drugs directed toward human leukocyte elastase and cathepsin G. We therefore sought to assess and compare relevant properties of both human and rat leukocyte elastase and cathepsin G. Some differences between the pairs of proteinases from the two species were found, however both pairs of enzymes displayed comparable specificity toward various natural (plant and animal) proteinase inhibitors and also toward specific peptide substrates and a serine proteinase-specific reagent. Such overlapping specificity implies similarity of reactive center topography and sequence homology around the extended substrate/inhibitor binding regions of these proteinases. This apparent homology leads us to conclude that a pharmacologically effective inhibitor of leukocyte proteinases in the rat would probably also be effective in man.