The Role of Elastase in the Digestion of E. coli Proteins by Human Polymorphonuclear Leukocytes I. Experiments in Vitro 1

Abstract

Summary

E. coli proteins were labelled by culturing the organisms in the presence of ³H-arginine. Sonicated preparations of bacteria were then incubated with water-soluble extracts of human PMN granules, and the rate of release of labelled peptides into the TCA-soluble phase was determined under different experimental conditions. Release was negligible at pH 3, but occurred at a significant rate at pH 7.6. Release at this pH was inhibited 82% and 94% by preincubation of the granule extract with 0.002 M AAACK or AAPACK respectively. The latter agents are specific, active-site directed, irreversible chloromethyl ketone elastase inhibitors. Granule extract preincubated with 0.002 M TLCK, a chloromethyl ketone trypsin inhibitor, retained full digestive activity against E. coli proteins. These in vitro results suggest that the elastase-like enzymes may contribute significantly to E. coli protein digestion following phagocytosis of this organism, and perhaps of other bacterial species, by human PMN.