Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.9 (enterokinase)
 675 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated and identified a new zymogen in human pancreatic tissue and fluid. It is secreted as a minor component of pancreatic juice and resembles the two known trypsinogen variants in many properties. Its electrophoretic mobility and isoelectric pH lie between those of the cationic and anionic trypsinogen variants, and we propose the name "mesotrypsinogen" for the new enzyme precursor. It is activated by enteropeptidase or trypsin, and the free enzyme possesses a substrate specificity similar to that of the trypsins. Its pH optimum is at 8.2, and it appears to require Ca2+ for full enzymatic activity. The molecular weight of the new enzyme is approximately 25,000, similar to that of the known trypsin variants. Its stability resembles that of anionic trypsin extending over a pH range of 4-8.5. Activity is lost gradually at pH 2. The enzyme is inactivated rapidly by diisopropylfluorophosphate, but in contrast to the trypsins, it reacts only slowly with tosyllysine chloromethylketone. Immunologically, it is different from the cationic trypsin variant with which it does not cross-react. The most remarkable property of mesotrypsin is its almost total resistance to biological trypsin inhibitors, such as pancreatic trypsin inhibitor, soybean, lima bean, ovomucoid inhibitor, alpha 1-antitrypsin, etc. It is capable of activating trypsinogen in the presence of excess pancreatic trypsin inhibitor and thus inducing activation of other pancreatic zymogens, but it also possesses the ability to degrade trypsinogen rapidly to inert products. The physiological or pathophysiological role of this unique enzyme remains to be explored.
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PMID:Mesotrypsin: a new inhibitor-resistant protease from a zymogen in human pancreatic tissue and fluid. 669 68

The cDNA encoding a novel isoform of human trypsinogen was identified. The isoelectric points of the proenzyme and active forms calculated from the deduced amino acid sequence are consistent with those of mesotrypsin(ogen), known to be an inhibitor-resistant trypsin isoform. The cDNA attached with a bacterial signal peptide sequence was expressed in Escherichia coli. The recombinant proenzyme purified from periplasm showed enterokinase-dependent activation similar to a major isoform of human trypsinogen. The enzyme was far less inhibited by trypsin inhibitors such as soybean trypsin inhibitor, aprotinin, or pancreatic secretory trypsin inhibitor than the control trypsin. A gel filtration assay showed that the enzyme and aprotinin did not form a stable complex. It is noteworthy that the amino acid at position 198, which is in close vicinity to the active Ser, is Arg while those of other major trypsins are all Gly. It is concluded that the cloned cDNA encodes human mesotrypsinogen, a unique isoform of trypsinogen with inhibitor resistance.
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PMID:Identification and expression of the cDNA-encoding human mesotrypsin(ogen), an isoform of trypsin with inhibitor resistance. 909 3

Certain serine proteases signal to cells by cleaving protease-activated receptors (PARs) and thereby regulate hemostasis, inflammation, pain and healing. However, in many tissues the proteases that activate PARs are unknown. Although pancreatic trypsin may be a physiological agonist of PAR(2) and PAR(4) in the small intestine and pancreas, these receptors are expressed by cells not normally exposed pancreatic trypsin. We investigated whether extrapancreatic forms of trypsin are PAR agonists. Epithelial cells lines from prostate, colon, and airway and human colonic mucosa expressed mRNA encoding PAR(2), trypsinogen IV, and enteropeptidase, which activates the zymogen. Immunoreactive trypsinogen IV was detected in vesicles in these cells. Trypsinogen IV was cloned from PC-3 cells and expressed in CHO cells, where it was also localized to cytoplasmic vesicles. We expressed trypsinogen IV with an N-terminal Igkappa signal peptide to direct constitutive secretion and allow enzymatic characterization. Treatment of conditioned medium with enteropeptidase reduced the apparent molecular mass of trypsinogen IV from 36 to 30 kDa and generated enzymatic activity, consistent with formation of trypsin IV. In contrast to pancreatic trypsin, trypsin IV was completely resistant to inhibition by polypeptide inhibitors. Exposure of cell lines expressing PAR(2) and PAR(4) to trypsin IV increased [Ca(2+)](i) and strongly desensitized cells to PAR agonists, whereas there were no responses in cells lacking these receptors. Thus, trypsin IV is a potential agonist of PAR(2) and PAR(4) in epithelial tissues where its resistance to endogenous trypsin inhibitors may permit prolonged signaling.
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PMID:Trypsin IV, a novel agonist of protease-activated receptors 2 and 4. 1472 24

Members of the trypsin-like and chymotrypsin-like kallikrein family are important in the desquamation process. In this study, we isolated cDNA clones encoding trypsinogen 4 (brain trypsinogen) and a previously unreported isoform of trypsinogen from a human keratinocyte cDNA library. The nucleotide sequence of the new isoform only differs from those of trypsinogen 3 (mesotrypsinogen) and trypsinogen 4 in an exon encoding the N-terminal region, indicating that this isoform is an alternative splicing variant of the mesotrypsinogen gene PRSS3. Both isoforms contained the sequence DDDDK-I, a putative cleavage site for activation by enteropeptidase. Thus, after activation, mesotrypsin would be produced. Immunohistochemical and in situ hybridization studies revealed that trypsinogens were expressed and localized in the upper epidermis, especially in the granular layer. In cultured keratinocytes, enteropeptidase mRNA was expressed at the confluent stage, and its expression was strongly upregulated after air exposure. Interestingly, it was synthesized and localized only at the granular layer, suggesting that the generation of active mesotrypsin is restricted to this layer. The enteropeptidase-cleavage product was also found at the same layer. When a skin equivalent model was cultured in the medium without air exposure, the cornified layer was not formed, and many cells expressed trypsinogens and enteropeptidase. Those cells were found to be TUNEL positive. Because mesotrypsin is resistant to naturally occurring trypsin inhibitors, confined expression of the isoforms of mesotrypsinogens and enteropeptidase may indicate that mesotrypsin is involved in keratinocyte terminal differentiation.
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PMID:Keratinocytes synthesize enteropeptidase and multiple forms of trypsinogen during terminal differentiation. 1992 34