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Isolated human protease proteins, nucleic acid molecules encoding human protease proteins, and uses thereof

Isolated human protease proteins, nucleic acid molecules encoding human protease proteins, and uses thereof description/claims

The present invention is in the field of protease proteins that are related to the carboxypeptidase subfamily, recombinant DNA molecules, and protein production. The present invention specifically provides novel peptides and proteins that effect protein cleavage/processing/turnover and nucleic acid molecules encoding such peptide and protein molecules, all of which are useful in the development of human therapeutics and diagnostic compositions and methods.

The proteases may be categorized into families by the different amino acid sequences (generally between 2 and 10 residues) located on either side of the cleavage site of the protease.

The proper functioning of the cell requires careful control of the levels of important structural proteins, enzymes, and regulatory proteins. One of the ways that cells can reduce the steady state level of a particular protein is by proteolytic degradation. Further, one of the ways cells produce functioning proteins is to produce pre or pro-protein precursors that are processed by proteolytic degradation to produce an active moiety. Thus, complex and highly-regulated mechanisms have been evolved to accomplish this degradation.

Proteases regulate many different cell proliferation, differentiation, and signaling processes by regulating protein turnover and processing. Uncontrolled protease activity (either increased or decreased) has been implicated in a variety of disease conditions including inflammation, cancer, arteriosclerosis, and degenerative disorders.

An additional role of intracellular proteolysis is in the stress-response. Cells that are subject to stress such as starvation, heat-shock, chemical insult or mutation respond by increasing the rates of proteolysis. One function of this enhanced proteolysis is to salvage amino acids from non-essential proteins. These amino acids can then be re-utilized in the synthesis of essential proteins or metabolized directly to provide energy. Another function is in the repair of damage caused by the stress. For example, oxidative stress has been shown to damage a variety of proteins and cause them to be rapidly degraded.

The International Union of Biochemistry and Molecular Biology (IUBMB) has recommended to use the term peptidase for the subset of peptide bond hydrolases (Subclass E.C 3.4.). The widely used term protease is synonymous with peptidase. Peptidases comprise two groups of enzymes: the endopeptidases and the exopeptidases, which cleave peptide bonds at points within the protein and remove amino acids sequentially from either N or C-terminus respectively. The term proteinase is also used as a synonym word for endopeptidase and four mechanistic classes of proteinases are recognized by the IUBMB: two of these are described below (also see: Handbook of Proteolytic Enzymes by Barrett, Rawlings, and Woessner AP Press, NY 1998). Also, for a review of the various uses of proteases as drug targets, see: Weber M, Emerging treatments for hypertension: potential role for vasopeptidase inhibition; Am J Hypertens 1999 November; 12(11 Pt 2): 139S-147S; Kentsch M, Otter W, Novel neurohormonal modulators in cardiovascular disorders. The therapeutic potential of endopeptidase inhibitors, Drugs R D 1999 April; 1(4):331-8; Scarborough R M, Coagulation factor Xa: the prothrombinase complex as an emerging therapeutic target for small molecule inhibitors, Enzym Inhib 1998; 14(1):15-25; Skotnicki J S, et al., Design and synthetic considerations of matrix metalloproteinase inhibitors, Ann N Y Acad Sci 1999 Jun. 30; 878:61-72; McKerrow J H, Engel J C, Caffrey C R, Cysteine protease inhibitors as chemotherapy for parasitic infections, Bioorg Med Chem 1999 April; 7(4):639-44; Rice K D, Tanaka R D, Katz B A, Numerof R P, Moore W R, Inhibitors of tryptase for the treatment of mast cell-mediated diseases, Curr Pharm Des 1998 October; 4(5):381-96; Materson B J, Will angiotensin converting enzyme genotype, receptor mutation identification, and other miracles of molecular biology permit reduction of NNT Am J Hypertens 1998 August; 11(8 Pt 2):138S-142S

Serine Proteases

The serine proteases (SP) are a large family of proteolytic enzymes that include the digestive enzymes, trypsin and chymotrypsin, components of the complement cascade and of the blood-clotting cascade, and enzymes that control the degradation and turnover of macromolecules of the extracellular matrix. SP are so named because of the presence of a serine residue in the active catalytic site for protein cleavage. SP have a wide range of substrate specificities and can be subdivided into subfamilies on the basis of these specificities. The main sub-families are trypases (cleavage after arginine or lysine), aspases (cleavage after aspartate), chymases (cleavage after phenylalanine or leucine), metases (cleavage after methionine), and serases (cleavage after serine).

A series of six SP have been identified in murine cytotoxic T-lymphocytes (CTL) and natural killer (NK) cells. These SP are involved with CTL and NK cells in the destruction of virally transformed cells and tumor cells and in organ and tissue transplant rejection (Zunino, S. J. et al. (1990) J. Immunol. 144:2001-9; Sayers, T. J. et al. (1994) J. Immunol. 152:2289-97). Human homologs of most of these enzymes have been identified (Trapani, J. A. et al. (1988) Proc. Natl. Acad. Sci. 85:6924-28; Caputo, A. et al. (1990) J. Immunol. 145:737-44). Like all SP, the CTL-SP share three distinguishing features: 1) the presence of a catalytic triad of histidine, serine, and aspartate residues which comprise the active site; 2) the sequence GDSGGP which contains the active site serine; and 3) an N-terminal IIGG sequence which characterizes the mature SP.

The SP are secretory proteins which contain N-terminal signal peptides that serve to export the immature protein across the endoplasmic reticulum and are then cleaved (von Heijne (1986) Nuc. Acid. Res. 14:5683-90). Differences in these signal sequences provide one means of distinguishing individual SP. Some SP, particularly the digestive enzymes, exist as inactive precursors or preproenzymes, and contain a leader or activation peptide sequence 3′ of the signal peptide. This activation peptide may be 2-12 amino acids in length, and it extends from the cleavage site of the signal peptide to the N-terminal IIGG sequence of the active, mature protein. Cleavage of this sequence activates the enzyme. This sequence varies in different SP according to the biochemical pathway and/or its substrate (Zunino et al, supra; Sayers et al, supra). Other features that distinguish various SP are the presence or absence of N-linked glycosylation sites that provide membrane anchors, the number and distribution of cysteine residues that determine the secondary structure of the SP, and the sequence of a substrate binding sites such as S′. The S′ substrate binding region is defined by residues extending from approximately +17 to +29 relative to the N-terminal I (+1). Differences in this region of the molecule are believed to determine SP substrate specificities (Zunino et al, supra).

Trypsinogens

The trypsinogens are serine proteases secreted by exocrine cells of the pancreas (Travis J and Roberts R. Biochemistry 1969; 8: 2884-9; Mallory P and Travis J, Biochemistry 1973; 12: 2847-51). Two major types of trypsinogen isoenzymes have been characterized, trypsinogen-1, also called cationic trypsinogen, and trypsinogen-2 or anionic trypsinogen. The trypsinogen proenzymes are activated to trypsins in the intestine by enterokinase, which removes an activation peptide from the N-terminus of the trypsinogens. The trypsinogens show a high degree of sequence homology, but they can be separated on the basis of charge differences by using electrophoresis or ion exchange chromatography. The major form of trypsinogen in the pancreas and pancreatic juice is trypsinogen-1 (Guy C O et al., Biochem Biophys Res Commun 1984; 125: 516-23). In serum of healthy subjects, trypsinogen-1 is also the major form, whereas in patients with pancreatitis, trypsinogen-2 is more strongly elevated (Itkonen et al., J Lab Clin Med 1990; 115:712-8). Trypsinogens also occur in certain ovarian tumors, in which trypsinogen-2 is the major form (Koivunen et al., Cancer Res 1990; 50: 2375-8). Trypsin-1 in complex with alpha-1-antitrypsin, also called alpha-1-antiprotease, has been found to occur in serum of patients with pancreatitis (Borgstrom A and Ohlsson K, Scand J Clin Lab Invest 1984; 44: 381-6) but determination of this complex has not been found useful for differentiation between pancreatic and other gastrointestinal diseases (Borgstrom et al., Scand J Clin Lab Invest 1989; 49:757-62).

Trypsinogen-1 and -2 are closely related immunologically (Kimland et al., Clin Chim Acta 1989; 184: 31-46; Itkonen et al., 1990), but by using monoclonal antibodies (Itkonen et al., 1990) or by absorbing polyclonal antisera (Kimland et al., 1989) it is possible to obtain reagents enabling specific measurement of each form of trypsinogen.

When active trypsin reaches the blood stream, it is inactivated by the major trypsin inhibitors alpha-2-macroglobulin and alpha-1-antitrypsin (AAT). AAT is a 58 kilodalton serine protease inhibitor synthesized in the liver and is one of the main protease inhibitors in blood. Whereas complexes between trypsin-1 and AAT are detectable in serum (Borgstrom and Ohlsson, 1984) the complexes with alpha-2-macroglobulin are not measurable with antibody-based assays (Ohlsson K, Acta Gastroenterol Belg 1988; 51: 3-12).

Inflammation of the pancreas or pancreatitis may be classified as either acute or chronic by clinical criteria. With treatment, acute pancreatitis can often be cured and normal function restored. Chronic pancreatitis often results in permanent damage. The precise mechanisms which trigger acute inflammation are not understood. However, some causes in the order of their importance are alcohol ingestion, biliary tract disease, post-operative trauma, and hereditary pancreatitis. One theory provides that autodigestion, the premature activation of proteolytic enzymes in the pancreas rather than in the duodenum, causes acute pancreatitis. Any number of other factors including endotoxins, exotoxins, viral infections, ischemia, anoxia, and direct trauma may activate the proenzymes. In addition, any internal or external blockage of pancreatic ducts can also cause an accumulation of pancreatic juices in the pancreas resulting cellular damage.

Anatomy, physiology, and diseases of the pancreas are reviewed, inter alia, in Guyton A C (1991) Textbook of Medical Physiology, WB Saunders Co, Philadelphia Pa.; Isselbacher K J et al (1994) Harrison's Principles of Internal Medicine, McGraw-Hill, New York City; Johnson K E (1991) Histology and Cell Biology, Harwal Publishing, Media Pa.; and The Merck Manual of Diagnosis and Therapy (1992) Merck Research Laboratories, Rahway N.J.

Metalloprotease

The metalloproteases may be one of the older classes of proteinases and are found in bacteria, fungi as well as in higher organisms. They differ widely in their sequences and their structures but the great majority of enzymes contain a zinc atom which is catalytically active. In some cases, zinc may be replaced by another metal such as cobalt or nickel without loss of the activity. Bacterial thermolysin has been well characterized and its crystallographic structure indicates that zinc is bound by two histidines and one glutamic acid. Many enzymes contain the sequence HEXXH, which provides two histidine ligands for the zinc whereas the third ligand is either a glutamic acid (thermolysin, neprilysin, alanyl aminopeptidase) or a histidine (astacin). Other families exhibit a distinct mode of binding of the Zn atom. The catalytic mechanism leads to the formation of a non covalent tetrahedral intermediate after the attack of a zinc-bound water molecule on the carbonyl group of the scissile bond. This intermediate is further decomposed by transfer of the glutamic acid proton to the leaving group.

Metalloproteases contain a catalytic zinc metal center which participates in the hydrolysis of the peptide backbone (reviewed in Power and Harper, in Protease Inhibitors, A. J. Barrett and G. Salversen (eds.) Elsevier, Amsterdam, 1986, p. 219). The active zinc center differentiates some of these proteases from calpains and trypsins whose activities are dependent upon the presence of calcium. Examples of metalloproteases include carboxypeptidase A, carboxypeptidase B, and thermolysin.

Metalloproteases have been isolated from a number of procaryotic and eucaryotic sources, e.g. Bacillus subtilis (McConn et al., 1964, J. Biol. Chem. 239:3706); Bacillus megaterium; Serratia (Miyata et al., 1971, Agr. Biol. Chem. 35:460); Clostridium bifermentans (MacFarlane et al., 1992, App. Environ. Microbiol. 58:1195-1200), Legionella pneumophila (Moffat et al., 1994, Infection and Immunity 62:751-3). In particular, acidic metalloproteases have been isolated from broad-banded copperhead venoms (Johnson and Ownby, 1993, Int. J. Biochem. 25:267-278), rattlesnake venoms (Chlou et al., 1992, Biochem. Biophys. Res. Commun. 187:389-396) and articular cartilage (Treadwell et al., 1986, Arch. Biochem. Biophys. 251:715-723). Neutral metalloproteases, specifically those having optimal activity at neutral pH have, for example, been isolated from Aspergillus sojae (Sekine, 1973, Agric. Biol. Chem. 37:1945-1952). Neutral metalloproteases obtained from Aspergillus have been classified into two groups, npI and npII (Sekine, 1972, Agric. Biol. Chem. 36:207-216). So far, success in obtaining amino acid sequence information from these fungal neutral metalloproteases has been limited. An npII metalloprotease isolated from Aspergillus oryzae has been cloned based on amino acid sequence presented in the literature (Tatsumi et al., 1991, Mol. Gen. Genet. 228:97-103). However, to date, no npI fungal metalloprotease has been cloned or sequenced. Alkaline metalloproteases, for example, have been isolated from Pseudomonas aeruginosa (Baumann et al., 1993, EMBO J. 12:3357-3364) and the insect pathogen Xenorhabdus luminescens (Schmidt et al., 1998, Appl. Environ. Microbiol. 54:2793-2797).

Metalloproteases have been divided into several distinct families based primarily on activity and structure: 1) water nucleophile; water bound by single zinc ion ligated to two His (within the motif HEXXH) and Glu, His or Asp; 2) water nucleophile; water bound by single zinc ion ligated to His, Glu (within the motif HXXE) and His; 3) water nucleophile; water bound by single zinc ion ligated to His, Asp and His; 4) Water nucleophile; water bound by single zinc ion ligated to two His (within the motif HXXEH) and Glu and 5) water nucleophile; water bound by two zinc ions ligated by Lys, Asp, Asp, Asp, Glu.

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