The complete amino acid sequence of human neutrophil elastase has been determined. The protein consists of 218 amino acid residues, contains two asparagine-linked carbohydrate side chains, and is joined together by four disulfide bonds. Comparison of the sequence to other serine proteinases indicates only moderate homology with porcine pancreatic elastase (43.0%) or neutrophil cathepsin G (37.2 %). In particular, many of the residues suggested to play important roles in the mechanism by which the pancreatic elastase functions are significantly changed in the neutrophil enzyme, indicating alternative types of binding with the human proteinase.Human neutrophils contain a battery of hydrolytic enzymes that normally are utilized for the degradation of foreign materials ingested as part of the phagocytic process (1). Although it is not completely clear whether such enzymes are also involved in tissue remodeling, this has been suggested as an alternate function (2). It is known that both neutrophil turnover and phagocytosis, themselves, do result in the leakage of enzymes into the extracellular milieu where they may cause extensive damage to connective tissue unless checked by controlling inhibitors (2). Indeed, a popular theory suggests that the development of pulmonary emphysema occurs as a result of insufficient levels of proteinase inhibitors (either locally or plasma-derived) whose primary functions are to inhibit these neutrophil enzymes (3). In particular, there is strong evidence that implicates neutrophil elastase as the proteinase most directly involved in abnormal lung connective tissue turnover. This is based on the fact that individuals devoid in the major controlling inhibitor of this enzyme, plasma a1-proteinase inhibitor, tend to develop obstructive lung disease (familial emphysema) much earlier than those with normal inhibitor levels (4).We have been interested in the potential function of both neutrophil elastase and cathepsin G in protein turnover. Both enzymes are capable of degrading a wide variety of substrates, including elastin, collagen, and proteoglycan, although it appears that elastase is more efficient in the turnover of such macromolecules (5, 6). Therefore, determination oftheir primary structures should be ofgreat value not only for understanding the mechanism by which each functions but also for developing specific inhibitors that might be useful in aiding in the control of their activities outside of the cell. This report describes the determination by conventional protein sequencing strategies of the primary structure of neutrophil elastase, a very basic glycoprotein that exists in a series of isoenzyme forms (7,8). In a separate report (9), a description of the primary structure of cathepsin G has been made by using a combination of recombinant DNA and protein-sequencing technology.MATERIALS AND METHODS Materials. Human neutrophil elastase was prepared from the granules of both normal and myeloid leukemia cells by affinity chromatography on Trasylol-Sepharose as described (1...

Tissue inhibitor of metalloproteinases (TIMP) from cultured bovine dental pulp inhibits human rheumatoid synovial matrix metalloproteinase 3 (MMP-3) with a stoichiometry of 1: 1 on a molar basis. Among the serine proteinases examined, human neutrophil elastase, trypsin and a-chymotrypsin destroyed the inhibitory activity of TIMP against MMP-3 by degrading the inhibitor molecule into small fragments. In contrast, the inhibitory activity of TIMP was not significantly reduced by the actions of cathepsin G, pancreatic elastase and plasmin. These data indicate that neutrophils which infiltrate tissues in various inflammatory conditions may play an important role in regulating TIMP activity in vivo through the action of neutrophil elastase.

The properties of plant purple acid phosphatases (PAPs), metallophosphoesterases present in some bacteria, plants and animals are reviewed. All members of this group contain a characteristic set of seven amino-acid residues involved in metal ligation. Animal PAPs contain a binuclear metallic center composed of two irons, whereas in plant PAPs one iron ion is joined by zinc or manganese ion. Among plant PAPs two groups can be distinguished: small PAPs, monomeric proteins with molecular mass around 35 kDa, structurally close to mammalian PAPs, and large PAPs, homodimeric proteins with a single polypeptide of about 55 kDa. Large plant PAPs exhibit two types of structural organization. One type comprises enzymes with subunits bound by a disulfide bridge formed by cysteines located in the C-terminal region around position 350. In the second type no cysteines are located in this position and no disulfide bridges are formed between subunits. Differences in structural organisation are reflected in substrate preferences. Recent data reveal in plants the occurrence of metallophosphoesterases structurally different from small or large PAPs but with metal-ligating sequences characteristic for PAPs and expressing pronounced specificity towards phytate or diphosphate nucleosides and inorganic pyrophosphate.

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