Specific cleavage of secretory leukoprotease inhibitor by neutrophil elastase and saliva.

In an attempt to explore the process of naturally occurring secretory leukoprotease inhibitor (SLPI) fragmentation, the cleavage profile of SLPI, which had been prepared by recombinant techniques, was investigated biochemically. Restricted fragments of SLPI were detected using SDS-PAGE after treatment with human neutrophil elastase (NE) or normal saliva and sequenced at their cleavage sites. Among these restricted fragments, two species of nearly half-length SLPIs that contained the C-terminal domain, (Arg58-Ala107)SLPI and (Arg59-Ala107)SLPI, were detected. They were both as active at inhibiting NE as the parent SLPI. These results suggest that functional SLPI derivatives may be generated physiologically in the respiratory tract under inflammatory and healthy conditions.