title: Cathepsin L inactivates alpha 1-proteinase inhibitor by cleavage in the reactive site region.
abstract: The lysosomal cysteine proteinases cathepsin L and cathepsin B were examined for their effect on the neutrophil elastase inhibitory activity of human alpha 1-proteinase inhibitor (alpha 1PI). Human cathepsin L catalytically inactivated human alpha 1PI by cleavage of the bonds Glu354-Ala355 and Met358-Ser359 (the serine proteinase inhibitory site). Cathepsin B did not inactivate alpha 1PI, even when equimolar amounts of enzyme were employed. Cathepsin L is the first human proteinase shown to catalytically inactivate alpha 1PI. These findings, in conjunction with other reports, suggest that alpha 1PI contains a proteolytically sensitive region encompassing residues 350-358. Taken together with the discovery of the elastinolytic activity of cathepsin L (Mason, R. W., Johnson, D. A., Barrett, A. J., and Chapman, H. A. (1986) Biochem. J. 233, 925-927), the present findings emphasize the possible importance of cathepsin L in the pathological proteolysis of elastin and diminish the role that can be attributed to cathepsin B in such processes.
mesh_terms: D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism*; D002401:Cathepsin B / Q000378:metabolism; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D003546:Cysteine Endopeptidases; D010450:Endopeptidases; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D008970:Molecular Weight; D011480:Protease Inhibitors / Q000378:metabolism*; D011485:Protein Binding; D000515:alpha 1-Antitrypsin
chemical_list: D001798:Blood Proteins; D011480:Protease Inhibitors; D000515:alpha 1-Antitrypsin; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L