Cathepsin L Inactivates α1-Proteinase Inhibitor by Cleavage in the Reactive Site Region

Document Type

Article

Publication Date

12-1-1986

Description

The lysosomal cysteine proteinases cathepsin L and cathepsin B were examined for their effect on the neutrophil elastase inhibitory activity of human α1-proteinase inhibitor (α1PI). Human cathepsin L catalytically inactivated human α1PI by cleavage of the bonds Glu354-Ala355 and Met358-Ser359 (the serine proteinase inhibitory site). Cathepsin B did not inactivate α1PI, even equimolar amounts of enzyme were employed. Cathepsin L is the first human proteinase shown to catalytically inactivate α1PI. These findings, in conjunction with other reports, suggest that α1PI contains a proteolytically sensitive region encompassing residues 350-358. Taken together with the discovery of the elastinolytic activity of cathepsin L, 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.

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