Identification of protease(s) capable of further degrading native 3/4- and 1/4-collagen fragments generated by collagenase from native type I collagen in human neutrophils.

The role of human neutrophil proteases in the further degradation of the native triple-helical characteristic cleavage products 3/4- and 1/4-collagen fragments generated by neutrophil interstitial collagenase from native type I collagen was studied. Purified human neutrophil collagenase did not further degrade the characteristic collagen fragments whether they were in triple-helical (native collagen) or random-coil (gelatin) conformation. Neutrophil extract treated with 1 mM phenylmercuric chloride (PMC) degraded native type I collagen at +37 degrees C producing multiple protein bands. Neutrophil extract at +18 degrees C in the presence of the serine protease inhibitors phenylmethylsulfonyl fluoride and banzamidine did not degrade native type I collagen. Inclusion of PMC to active latent collagenase caused neutrophil extract to degrade native type I collagen to 3/4- and 1/4-fragments. In addition, native 3/4- and 1/4-fragments were further degraded in a time-dependent manner by PMC-treated neutrophil extract. Both native 3/4- and 1/4-collagen fragments were degraded by specific rather than by multiple cleavage. Further fragmentation was inhibited by divalent cation chelators EDTA and 1,10-phenanthroline. The results indicate the presence of latent metalloprotease(s), as distinct from collagenase, gelatinase and serine proteases, that are capable of further degrading by specific cleavage both native 3/4- and 1/4-collagen fragments generated by collagenase in human neutrophils. The enzyme(s) may augment the action of collagenase and other neutral proteases in connective tissue destruction associated with the etiopathogenesis of periodontal diseases.