Cathepsin G degrades denatured collagen.

Neutrophils are known to contain several metalloproteinases that can damage collagen, a major structural component of the extracellular matrix. Here a neutrophil serine proteinase secreted from activated neutrophils was shown to cleave denatured collagen (gelatin). This serine proteinase was not inhibited by synthetic inhibitors of elastase (elastatinal or Me-O-suc-Ala-Pro-Val-CH2Cl). However, a synthetic inhibitor of cathepsin G (Z-Gly-Leu-Phe-CH2Cl) was able to inhibit the serine proteinase having gelatinolytic activity, indicating that cathepsin G, a major serine proteinase, from neutrophils is responsible for cleaving gelatin. Purified cathepsin G was also shown to degrade gelatin. In further experiments, oxidized glutathione was able to enhance the gelatinolytic activity of cathepsin G. These results show that cathepsin G is capable of cleaving denatured collagen, and its activity is enhanced or stabilized in the presence of glutathione. The data support the concept that cathepsin G released from neutrophils could play a major role in degrading collagen during inflammation and may in part account for the degradation of extracellular matrix during inflammation.