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)

Modified trypsin kallikrein inhibitor (I*), with the reactive-site peptide bond Lys-15--Ala-16 split, reacts with alpha-chymotrypsin (E) via an intermediate X to the stable tetrahedral complex C:E + I in equilibrium X leads to C. Formation X constitutes a fast pre-equilibrium (equilibrium constant Kx = 7 X 10(-5) M, association rate constant kx = 4 X 10(3)M-1s-1) to the slow reaction X leads to C (rate constant kc = 2 X 10(-3) s-1), all values at pH 7.5. No intermediate X is observed when alpha-chymotrypsin reacts with I*-OMe in which the carboxyl group of Lys-15 is esterified by methanol. This observation as well as the different pH dependence of the overall association rate constants in the case of I* and I*-OMe indicate tha formation of X precedes formation of the acyl enzyme in the catalytic pathway. The data are compared to the similar results obtained with beta-trypsin and I* or I*-OMe.
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PMID:Kinetics of the interaction of alpha-chymotrypsin with trypsin kallikrein inhibitor (Kunitz) in which the reactive-site peptide bond Lys-15--Ala-16 is split. 2 64

Three new protease inhibitors were isolated and purified about 200-fold from hemolymph of silkworm larvae, Bombyx mori, using ion-exchange and affinity chromatography. Two of the three inhibitors were basic proteins (SCI-I had pI 9.4 and SCI-II had pI 9.6) and one was acidic (SCI-III had pI 4.0). The molecular weight of each inhibitor was determined to be 7,000 by the sedimentation equilibrium method. The amino acid composition of the inhibitors were similar except for the contents of Asp, Glu, Ile, Leu, and Lys. Val, His, and Trp were not present in the inhibitors and Met appeared only in SCI-III. The CD spectra of the inhibitors were all similar and indicated a low content of alpha-helical structure (10% at most). Each inhibitor could inhibit the protease and esterase activities of bovine alpha-chymotrypsin at a one-to-one molar ratio, and the dissociation constants were 3.1 X 10(-9)M for SCI-I and II and 1.3 X 10(-8)M for SCI-III. Only SCI-II showed a weak inhibitory activity against bovine trypsin. Subtilisin BPN' and papain were not inhibited by these inhibitors.
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PMID:Chymotrypsin inhibitors from hemolymph of the silkworm, Bombyx mori. 2 86

The Vicia angustifolia proteinase inhibitor was incubated with p-toluenesulfonyl-L-phenylalanine chloromethyl ketone-trypsin (EC 3.4.21.4) and a main product was isolated. The purified product was different to the first trypsin-modified V. angustifolia inhibitor. The C-terminal residues of the new derivative were arginine, which was also the C-terminal of the cleaved antitryptic site; lysine was a newly exposed C-terminal. These results suggest that the new derivative lacks the C-terminal portion of the native inhibitor, which has asparagine at its C-terminus. The liberated C-terminal peptide had the following amino acid sequence: H-Glu-Glu-Val-Ile-Lys-Asn-OH. The derivative lacking the C-terminal hexapeptide still possesses inhibitory activities against trypsin and alpha-chymotrypsin (EC 3.4.21.1), however, its antichymotryptic activity was inactivated by incubation with chymotrypsin at pH 8.0.
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PMID:Isolation and activities of the trypsin-modified Vicia angustifolia proteinase inhibitor lacking carboxyl-terminal hexapeptide. 3 67

The steady-state kinetics of plasmin- (EC 3.4.21.7) and trypsin-catalysed (EC 3.4.21.4) hydrolysis of Bz-L-Phe-Val-Arg-pNA, Bz-D-Phe-Val-Arg-pNA, L-Phe-Val-Arg-pNA, D-Phe-Val-Arg-pNA and D-Val-Leu-Lys-pNA were investigated in the pH range 6-9. The pH dependences of the kinetic parameters correspond with the effects of catalytically essential ionizations in the enzymes, except for reactions with L- and D-Phe-Val-Arg-pNA, in which protonation of the NH2-terminal alpha-amino groups (pK = 7.0) shows some inhibitory effect. The reactions of plasmin and trypsin with p-nitroanilides show kc values similar to those normally found with specific ester substrates, indicating that the deacylation steps of the reactions are rate determining.
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PMID:Steady-state kinetics of plasmin- and trypsin-catalysed hydrolysis of a number of tripeptide-p-nitroanilides. 3 47

Trypanosoma congolense Broden, an intravascular parasite, binds to vessel walls and erythrocytes of infected hosts. In an attempt to characterize T. congolense adhesion to host cells, an in vitro assay was devised. It was shown in the in vitro experiments that T. congolense binds to bovine, sheep, and goat erythrocytes, but not always to erythrocytes of rats, mice, rabbits, horses or humans. Only the anterior part of live trypanosomes adheres to erythrocytes, and the attachment site on the trypanosomes is destroyed by trypsin and chymotrypsin-trypanosomes did not adhere to bovine erythrocytes that had been incubated with neuraminidase, sodium periodate and poly-L-lysine. The foregoing experiments suggest that the surface of T. congolense contains a protein-associated site which binds to sialic acid of some host cells. This surface site is most likely responsible for attachment to blood vessels in vivo.
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PMID:In vitro binding of Trypanosoma congolense to erythrocytes. 3 67

Methionyl-tRNA synthetase from Escherichia coli can react with periodate-treated tRNA to form a Schiff's base through the epsilon-amino group of a lysine within the enzymic active center and the 2',3'-aldehyde groups created at the 3'-terminal ribose of tRNA. At alkaline pH, the Schiff's base equilibrium can be continuously and specifically displaced by reduction in situ with sodium cyanohydridoborate, which on the other hand leaves intact the reacting aldehyde groups of oxidized tRNA. The effects of temperature, pH and of reducing agent concentration on the rate and extent of reduction of the Schiff's base are analysed. Conditions are described (37 degrees C, pH 8.0, in the presence of 1 mM cyanohydridoborate) which allowed rapid and complete conversion of the monomeric trypsin-modified methionyl-tRNA synthetase into its 1:1 covalent complex with tRNAfMet.
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PMID:Complete inactivation and labeling of methionyl-tRNA synthetase by periodate-treated initiator tRNA in the presence of sodium cyanohydridoborate. 4 39

Porcine plasmin (EC 3.4.21.7) is obtained from plasminogen activated by human urokinase. This enzyme can bind, in an equimolecular ratio, to an alpha2-macroglobulin isolated from porcine serum. The number of active sites of plasmin has been determined through a burst titration of nitroaniline during the presteady-state hydrolysis of an amide substrate (N-alpha-carbobenzoxy-L-arginine-p-nitroanilide). The kinetic constants relative to a very sensitive ester substrate (N-alpha-carbobenzoxy-L-lysine nitrophenylester) hydrolysis have been measured. The binding of plasmin to alpha2-macroglobulin results in a complete inhibition of proteolytic activity, a reduction of active sites number and a decrease of esterolytic activity towards this substrate. In the complex, the residual activity (about 60%) is protected from protein inhibitors. Absorbance difference spectra show that 1 mol of alpha2-macroglobulin binds 1 mol of plasmin and 2 mol of trypsin. When plasmin is first bound to alpha2-macroglobulin, only 1 mol of trypsin can gain access tothe second site without removing the plasmin, showing that a steric hindrance is implicated in the inhibition performed by alpha2-macroglobulin binding.
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PMID:[Study of the complex between porcine plasmin and alpha2-macroglobulin (author's transl)]. 5 8

An immunopeptide bearing a3 allotypic determinant(s) was isolated from the gamma chain of an a3 homozygous rabbit (G222-2) immunized with type III pneumococcal vaccine. Immunocogical properties of peptides were studied using a radioimmunoassay that involved inhibition by these peptides of a reaction between 125I-labeled anti-a3 antibody and Sepharose-bound a3 immunoglobulin G (IgG). The gamma chain was isolated from IgG of restricted heterogeneity and then citraconylated and digested with trypsin. The tryptic digest (TD1) was passed through an anti-a3 immunoabsorbent column either directly or after an intermediate step of Sephadex G-75 chromatography. The bound peptides (T1) were eluted with 0.1 M acetic acid and further digested with trypsin. The digest (TD2) was again run on the anti-a3 immunoabsorbent column to purify the bound immunopeptide T2. In the radioimmunossay this immunopeptide was found to have major a3 determinant(s). Its molecular weight was found to be approximately 6,000, which decreased to about 3,000 after reduction and alkylation. These data, together with NH2- and COOH-terminal analyses and cysteine peptide mapping, demonstrated that T2 is composed of two polypeptide chains linked by a disulfide bond, one from the cysteine 22 region having lysine at the COOH terminus and the other from the cysteine 92 region arginine at the COOH terminus. The lysine peptide was separated from the arginine peptide and its NH2-terminal sequence was found to be Gly-Asx-Glx-Ser-Thr-Cys. Since the cysteine is at position 22, the lysine peptide starts at position 17. It has approximately 22 residues. The framework sequence from 17 to 20 is different from those reported so far. In addition, the heavy chain used in these studies has some other unusual features including a histidine, probably in the first hypervariable region. The presence of histidine in the first hypervariable region of rabbit heavy chain has not been reported previously. The other peptide which is about 30 amino acids in length and ends with arginine 94, probably includes positions 67, 70, 71, 84, and 85 that are believed to have substitutions correlating with a allotypes. In a hypothetical three-deminsional model of the Fv portion of rabbit anti-SIII antibody BS-5, residues 17 to 33 of the lysine peptide and 67 to 79 and 84 to 85 which may be present in the arginine peptide are fully exposed on the surface and are far removed from the antibody combining site.
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PMID:Studies on the structural localization of rabbit H chain allotypic determinants controlled by the a locus. Purification and immunological properties of an immunopeptide bearing a3 allotypic determinants. 6 65

A method is described for the recovery of purified T-antigen from crude trypsin extracts of an avirulent strain of M-1 protein deficient, T-type 1 group A Streptococcus. The purified T-antigen was resistant to enzymatic degradation with trypsin and pepsin, formed a single precipitin line with standard T-1 antiserum, failed to react with antisera for teichoic acid, group A carbohydrate, and cross-reactive protein antigens, stimulated only a single precipitin system when rabbits were immunized, contained glycine, aspartic acid, glutamic acid, lysine, and serine as the five most predominant amino acids, and consisted of subunit size isomers.
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PMID:Purification and characterization of group A streptococcal T-1 antigen. 7 Apr 8

Rat vaginal epithelial cells have trypsin-like activity as shown by the formation of a colored product when the cells are incubated with alpha-N-methyl alpha-N-toxyl-L-lysine beta-naphthol ester and hexazotized pararosanilin. This enzyme activity in vaginal smears is maximal at proestrus, i.e., the day in the 5-day estrus cycle when plasma estrogen is maximal. Only the rounded nucleated epithelial cells present at late diestrus, proestrus and early estrus demonstrate the trypsin-like enzyme activity. These are the cells that stain blue in the Papanicolaou method. Preincubation of cell suspensions with the serine protease inhibitor, p-nitrophenyl p-guanidino benzoate, prevented the enzyme staining reaction, further demonstrating the trypsin-like nature of the cellular enzyme. The advantages of this enzyme staining technique over the fibrin plate method for the demonstration of trypsin-like enzymes in cells are increased resolution and ability to show trypsin inhibitor effects.
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PMID:Trypsin-like activity in the vaginal epithelial cells of the rat. 7


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