Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human intracellular serine proteinase inhibitor, proteinase inhibitor 6 (PI-6), was expressed in the methylotropic yeast Pichia pastoris. The PI-6 cDNA was modified to encode six histidine residues immediately after the initiation codon, and was placed under the control of the P. pastoris alcohol oxidase promoter in the vector pHIL-D2. On the methanol induction, active recombinant PI-6 was produced within the yeast cells, and following cell lysis, was separated from yeast proteins by affinity chromatography using nickel nitrilo-tri-acetic acid (NTA) resin. The interaction of recombinant PI-6 with a range of serine proteinases was studied. Second order association rate constants (ka) were derived for the interaction with trypsin (1.8 x 10(6) M-1 s-1), thrombin (1.2 x 10(5) M-1 s-1), urokinase plasminogen activator (4.0 x 10(4) M-1 s-1), plasmin (1.3 x 10(6) M-1 s-1), and activated protein C (7.5 x 10(3) M-1 s-1). By monitoring complex formation, recombinant PI-6 was also shown to interact with factor Xa. No complex formation was observed with chymotrypsin, human leukocyte elastase, cathepsin G and tissue plasminogen activator, although PI-6 is apparently a substrate for chymotrypsin, leukocyte elastase and cathepsin G.
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PMID:Production and characterization of recombinant human proteinase inhibitor 6 expressed in Pichia pastoris. 754 63

Phage displaying APPI Kunitz domain libraries have been used to design potent and selective active site inhibitors of human plasma kallikrein, a serine protease that plays an important role in both inflammation and coagulation. Selected clones from two Kunitz domain libraries randomized at or near the binding loop (positions 11-13, 15-19, and 34) were sequenced following five rounds of selection on immobilized plasma kallikrein. Invariant preferences for Arg at position 15 and His at position 18 were found, whereas His, Ala, Ala, and Pro were highly preferred residues at positions 13, 16, 17, and 19, respectively. At position 11 Pro, Asp, and Glu were favored, while hydrophobic residues were preferred at position 34. Selected variants, purified by trypsin affinity chromatography and reverse phase high performance liquid chromatography, potently inhibited plasma kallikrein, with apparent equilibrium dissociation constants (Ki*) ranging from approximately 75 to 300 pM. From sequence and activity data, consensus mutants were constructed by site directed mutagenesis. One such mutant, KALI-DY, which differed from APPI at 6 key residues (T11D, P13H, M17A, I18H, S19P, and F34Y), inhibited plasma kallikrein with a Ki* = 15 +/- 14 pM, representing an increase in binding affinity of more than 10,000-fold compared to APPI. Similar to APPI, the variants also inhibited Factor XIa with high affinity, with Ki* values ranging from approximately 0.3 to 15 nM; KALI-DY inhibited Factor XIa with a Ki* = 8.2 +/- 3.5 nM. KALI-DY did not inhibit plasmin, thrombin, Factor Xa, Factor XIIa, activated protein C, or tissue factor. Factor VIIa. Consistent with the protease specificity profile, KALI-DY did not prolong the clotting time in a prothrombin time assay, but did prolong the clotting time in an activated partial thromboplastin time assay > 3.5-fold at 1 microM.
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PMID:Potent and selective Kunitz domain inhibitors of plasma kallikrein designed by phage display. 759 8

Two kinds of proteinases, type-I and type-II, were purified or partially purified from salted muscle of anchovy, Engraulis japonica. Mol. wts. of type-I and type-II proteinases were estimated to 25,000 and 37,000, respectively, on electrophoretic analysis. Both proteinases strongly hydrolyzed synthetic tri or tetrapeptide substrates specific to trypsin, alpha-thrombin, and an activated protein C, while they hardly hydrolyzed Arg-MCA and benzoyl Arg-MCA derivatives. The proteinases were inhibited by common trypsin inhibitors. Optimal pH for the proteinase activities were pH 6.8 (type-I) and pH 7.0 to 7.5 (type-II), and the proteinases showed the highest activities at 45 degrees C (type-I) and 50 degrees C (type-II). The N-terminal amino acid sequence of type-I proteinase, 1I-2V-3G-4G ... (29 residues were identified), was significantly similar to sequences of trypsins and tryptases. Based on these findings, both proteinases were presumed to be kinds of tryptases in E. japonica muscle.
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PMID:Two kinds of neutral serine proteinases in salted muscle of anchovy, Engraulis japonica. 761 98

Z-D-Phe-Pro-boroMpg-OPin (9a)1,2 has been shown previously to be a highly specific inhibitor of thrombin in spite of lacking an arginine-like guanidino group at the P1 site. A range of compounds have been synthesized based upon this lead compound, varying the neutral side chain at the P1 site. Of the 20 examples based upon the structures at P2 and P3 of Z-D-X-Pro (X being Phe or beta,beta-diphenylalanine), all were found to be effective inhibitors of thrombin (Ki's between 10 and 100 nM). Furthermore all exhibited a high specificity toward thrombin having values for a Ki(trypsin)/Ki(thrombin) ratio of between 10- and 100-fold. High ratio values were found for a number of the compounds tested against a range of serine proteinases (plasmin, factor Xa, kallikrein, urokinase, protein Ca, chymotrypsin, elastase, and cathepsin G). As far as potency toward thrombin, compounds containing the methoxypropyl group at P1 were favored over those with a methoxy grouping on a shorter alkyl chain (8) or without the methoxy group (1-5). The compounds display potent anticoagulant activity with values for 18 in thrombin time of 0.63 microM and in activated partial thromboplastin time of 2.0 microM. 11B NMR has been used to confirm interaction of the boron atom with the active site. From the high specificity shown with all the compounds we propose that the compounds, constitute a new class of thrombin inhibitors.
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PMID:Characterization of a class of peptide boronates with neutral P1 side chains as highly selective inhibitors of thrombin. 773 10

Binding Ca2+ to a high affinity site in protein C and Gla-domainless protein C (protein C lacking residues 1-44) results in a conformational change that is required for activation by the thrombin-thrombomodulin complex, the natural activator of protein C. Protein C modeling studies suggested the single high affinity Ca2+ binding-site might be present in a loop in the protease domain and involve Glu-70 and -80 (chymotrypsin numbering system). This loop, which is a known Ca(2+)-binding site in trypsin, is also conserved in other coagulation proteases, including factors VII, IX,and X. In thrombin, which does not bind Ca2+, Glu-70 is replaced by Lys, creating an internal salt bridge with Glu-80. We constructed and expressed a Gla-domainless protein C mutant in which Glu-80 is replaced with Lys. The activation of the resultant mutant is accelerated by thrombomodulin in a Ca(2+)-independent fashion. Unlike wild type Gla-domainless protein C, Ca2+ no longer inhibits activation of the mutant by free thrombin, and Ca2+ stimulation of chromogenic activity is also absent. The characteristic Ca(2+)-dependent quenching of Gla-domainless protein C intrinsic fluorescence is also absent in the mutant. We conclude that the high affinity Ca(2+)-binding site in protein C critical for zymogen activation involves Glu-80. The Glu-80 to Lys mutation probably results in a salt bridge with Glu-70 that stabilizes protein C zymogen in a conformation similar, if not identical, to the Ca(2+)-stabilized conformation favorable for rapid activation by the thrombin-thrombomodulin complex.
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PMID:Mutation of Glu-80-->Lys results in a protein C mutant that no longer requires Ca2+ for rapid activation by the thrombin-thrombomodulin complex. 790 67

Three-dimensional structural analysis of physiologically important serine proteases is useful in identifying functional features relevant to the expression of their activities and specificities. The human serine protease anticoagulant protein C is currently the object of many genetic site-directed mutagenesis studies. Analyzing relationships between its structure and function and between naturally occurring mutations and their corresponding clinical phenotypes would be greatly assisted by a 3-dimensional structure of the enzyme. To this end, molecular models of the protease domain of protein C have been produced using computational techniques based on known crystal structures of homologous enzymes and on protein C functional information. The resultant models corresponding to different stages along the processing pathway of protein C were analyzed for structural and electrostatic differences arising during the process of protein C maturation and activation. The most satisfactory models included a calcium ion bound to residues homologous to those that ligate calcium in the trypsin structure. Inspection of the surface features of the models allowed identification of residues putatively involved in specific functional interactions. In particular, analysis of the electrostatic potential surface of the model delineated a positively charged region likely to represent a novel substrate recognition exosite. To assist with future mutational studies, binding of an octapeptide representing a protein C cleavage site of its substrate factor Va to the enzyme's active site region was modeled and analyzed.
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PMID:Models of the serine protease domain of the human antithrombotic plasma factor activated protein C and its zymogen. 800 77

Potent active-site inhibitors of human tissue factor-Factor VIIa (TF.FVIIa) have been selected from Alzheimer's amyloid beta-protein precursor inhibitor (APPI) Kunitz domain libraries displayed on phage. Eight randomized positions on the extended primary binding loop (P5 through P4') and positions 34 and 39 were examined in three separate libraries. Libraries contained from 3.2 x 10(5) to 3.2 x 10(6) potential variants resulting from replacing up to 5 positions with all 20 amino acids. Following 4 rounds of selection against FVIIa associated with immobilized tissue factor (TF), 12 clones from each library were sequenced. Variants were purified by trypsin affinity chromatography and reverse-phase high performance liquid chromatography, and characterized for their ability to inhibit TF.FVIIa chromogenic activity. Measured apparent equilibrium dissociation constants (Ki*) ranged from about 10 to 500 nM. From sequence and activity data, an overall consensus sequence, TF7I-C, was constructed by site-directed mutagenesis. TF7I-C differed from APPI at 4 key residues, T11P, M17L, S19L, and G39Y, and inhibited TF.FVIIa with a Ki* = 1.9 +/- 0.4 nM, which represented an increase in binding affinity of more than 150-fold compared to APPI. At 40 microM, TF7I-C prolonged the clotting times 3.5-fold in a prothrombin time assay and > 10-fold at 7 microM in an activated partial thromboplastin time assay. Prolongation of the activated partial thromboplastin time correlates with potent inhibition of FXIa (Ki* = 0.8 nM) and plasma kallikrein (Ki* = 1.2 nM). TF7I-C also inhibited plasmin (Ki* = 40 nM) and FXa (Ki* = 55 nM), but not activated protein C, thrombin, or FXIIa (Ki* > 10 microM each).
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PMID:Kunitz domain inhibitors of tissue factor-factor VIIa. I. Potent inhibitors selected from libraries by phage display. 807 37

Human activated protein C (APC) has been shown to be physiologically susceptible to inhibition by the abundant serpin inhibitor alpha-1-anti-trypsin (AAT). Studies on the inactivation by AAT [Heeb, M. J., & Griffin, J. H. (1988) J. Biol. Chem. 263, 11613-11616] have shown that the calculated rate of this inactivation matches that of the observed half-life of APC in vivo [Wydro, R., Oppenheimer, C., Rodger, R., & Miemi, S. (1988) Clin. Res. 36, 329A] and complex formation therefore probably represents a physiologic regulation process for APC. In this study we observed that bovine APC, in contrast to human APC, is nearly completely resistant to inactivation by human AAT. An additional difference between human and bovine APC is that human APC is a potent anticoagulant in human plasma, whereas bovine APC is only minimally active in human plasma. These functional differences exist despite considerable structural similarity between the human and bovine molecules. In order to identify specific molecular regions responsible for function, a chimeric molecule consisting of the light chain of human protein C (PC) and the heavy chain of bovine PC was constructed, expressed, and characterized. The activated chimeric PC is similar to human APC in having potent anticoagulant activity in human plasma, but displays nearly identical resistance to AAT inhibition with the bovine molecule. The similarity between the chimeric and bovine molecules in resistance to AAT inhibition indicates that the structural determinants for inhibitor interactions reside within the heavy chain (serine protease) domain.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Resistance to inhibition by alpha-1-anti-trypsin and species specificity of a chimeric human/bovine protein C. 811 Jul 91

Ecotin, a serine protease inhibitor found in the periplasm of Escherichia coli, has been characterized as an extremely potent anticoagulant and reversible tight-binding inhibitor of human factor Xa (FXa). The ecotin gene was cloned by PCR, highly expressed in E. coli, and purified from the E. coli periplasm. The binding of ecotin to FXa was stoichiometric with an equilibrium dissociation constant Ki of 54 pM. The association rate constant was 1.35 x 10(6) M-1 s-1, and the dissociation rate constant, measured in the presence of human leukocyte elastase (HLE) to prevent reassociation of ecotin with FXa, was 6.5 x 10(-5) s-1. Ecotin prolonged clotting time ca. 10-fold at 0.3 microM and at 2 microM in activated partial thromboplastin time and prothrombin time assays, respectively. Ecotin did not effectively inhibit the human plasma proteases thrombin, tissue factor.factor VIIa, factor XIa, activated protein C, plasmin, or tissue plasminogen activator (t-PA); however, it did potently inhibit factor XIIa, plasma kallikrein, HLE, and bovine trypsin and chymotrypsin. Coincubation of ecotin and FXa at 10 microM each resulted in a (ecotin)2.(FXa)2 complex as determined by gel filtration. Dimerization of ecotin alone was measured by fluorescence titration which yielded a Kd of ca. 390 nM. FXa cleaved ecotin slowly at pH 4.0 between M84 and M85. Replacement of the P1 Met84 residue with Arg and Lys led to FXa inhibitors with Ki values of 11 and 21 pM, respectively. The P1 Arg and Lys mutants also significantly inhibited thrombin, factor XIa, activated protein C, plasmin, factor XIIa, kallikrein, and bovine trypsin and chymotrypsin but did not inhibit tissue factor.factor VIIa, t-PA, or HLE.
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PMID:Ecotin is a potent anticoagulant and reversible tight-binding inhibitor of factor Xa. 814 99

Protein C inhibitor (PCI) is a heparin-binding plasma serine proteinase inhibitor (serpin) which is thought to be a physiological regulator of activated protein C. We are using recombinant PCI (rPCI) to study structural determinants of target proteinase specificity. A cDNA encoding full-length PCI has been expressed as a fully active proteinase inhibitor using Autographa californica nuclear polyhedrosis virus (baculovirus). rPCI was expressed maximally 4 days after infection and could be expressed either in Sf9 or High-Five cells. rPCI bound heparin and was conveniently purified with heparin-Sepharose (eluting > 0.5 M NaCl). The rPCI formed sodium dodecyl sulfate-polyacrylamide gel electrophoresis-stable complexes with thrombin and activated protein C (APC). The inhibitory properties of wild-type rPCI and plasma-derived PCI are essentially the same either in the absence or presence of heparin with thrombin, APC, trypsin, and urokinase. The residues Phe353-Arg354-Ser355 (P2-P1-P1') constitute part of the reactive site loop of PCI with the Arg-Ser peptide bond being cleaved by the proteinase. Using site-directed mutagenesis we studied the contribution of the reactive site FRS for proteinase inhibition in rPCI. Changing the P1 residue Arg354-->Met generated a reactive site similar to alpha 1-proteinase inhibitor which was a much poorer inhibitor of thrombin, APC, trypsin, and urokinase. Changing the P2 residue Phe353-->Gly generated a mutant with a reactive site like antithrombin which was better at inhibiting thrombin or urokinase, but was much less active with APC or trypsin. Changing the P1' residue Ser355-->Met generated a reactive site like plasminogen activator inhibitor-1 and this protein inhibits all the proteinases essentially like wild-type rPCI. These results show the importance of PCI's Phe353 (P2) and Arg354 (P1) in target proteinase specificity, and they further support the concept of reactive site sequences determining serpin function.
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PMID:Mutagenesis of recombinant protein C inhibitor reactive site residues alters target proteinase specificity. 820 90


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