Enzymatic and molecular biochemical characterizations of human neutrophil elastases and a cathepsin G-like enzyme

Human neutrophil elastase (HNE, EC 3. 4. 21. 37) is a causative factor of i nflammatory diseases, including emphysema and rheumatoid arthritis. Enzymat ic characterization is important for the development of new drugs involved in the regulation of this enzyme, In this study, we investigated the enzyma tic and biochemical properties of five different elastolytic enzymes, with a molecular mass between 24 kDa and 72 kDa, Three elastases, molecular mass es of 27, 29, 31 kDa, might be elastase isozymes that have the same NH2-ter minal amino acid sequences of Ile-Val-Gly-Gly-Arg-Arg-Ala. The 24-kDa enzym e, which showed the identical NH2-terminal amino acid sequences to elastase , was a degraded fragment of native elastase, The elastolytic activity was conserved at the 6/7 domain of the NH2-terminal region. The inhibitory char acteristics of PMSF, DipF were the same as those of native elastases, The 7 2-kDa molecule, which showed elastolytic activity, might be a trimer formed between native elastases (31 kDa and 29 kDa) and a cathepsin G-like enzyme , which did not show elastolytic activity but enhanced the elastolytic acti vity of neutrophil elastase, Although this cathepsin C-like enzyme showed w eak cathepsin G activity, it has distinguishable NH2-terminal sequences of Ile-Val-Gly-Gly-Ser-Arg-Ala- from those of elastase or cathepsin G, The pot entiation of elastolytic activity could he a result of the trimerization of native elastase with a cathepsin G-like enzyme, and was then weakly inhibi ted by serine protease inhibitors, such as PMSF, DipF, Therefore, we sugges t the cathepsin G-like enzyme to be a novel enzyme, which has an important role in the development of inflammation.