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 effects of protein modification procedures on the biologically most important properties of cholera toxin, i.e. the toxic activity, the GM1 receptor-binding capacity and the antigenic (antibody-fixing) properties, have been studied quantitatively using microgram amounts or less of toxin protein. Most of the 24 group-specific reagents used had either no inhibitory effect on the toxic or the combination of GM1-binding and antibody-fixing properties of cholera toxin, or they had a concomitant inhibitory effect on these activities. Separate testing of GM1- and antibody-binding revealed a close, but not absolute, structural association between these properties, Amino group reactive substances were particularly effective in decreasing the GM1-binding activity, while leucine aminopeptidase had no effect. This suggests that lysine residues may be involved in binding toxin to the acidic GM1 receptor. Sodium dodecylsulphate and mercaptoethanol, which caused dissociation of the subunits of cholera toxin as indicated by polyacrylamide gel electrophoresis, abolished toxicity without inhibiting the concomitant GM1- and antibody-binding properties of the toxin. Similar differential effects were also obtained with three reagents which did not seem to change the aggregation state of the toxin. These substances all had specificity for arginine, suggesting that arginyl residues of the toxin molecule may be involved in a 'toxic site' distinct from the receptor-binding site(s). A selective effect on the toxic site was also found by treating the toxin with carboxypeptidase or trypsin in the presence of urea; in the absence of urea no enzymic effect on any toxin property was noted.
J Gen Microbiol 1975 Dec
PMID:Protein reagent modification of cholera toxin: characterization of effects on antigenic, receptor-binding and toxic properties. 120 72

The properties of the low threshold Ca current (ICaT) in bullfrog (Rana catesbeiana) isolated atrial cardiomyocytes were studied using the whole-cell recording patch-clamp technique and compared with those of the high threshold Ca current (ICaL). In 91% of atrial cells we observed both ICaT and ICaL when collagenase and trypsin were used to dissociate the cells. But when pronase was used, only 30% of the cells exhibited ICaT. ICaT was never found in ventricular cells. ICaT could be investigated more easily when ICaL was inhibited by Cd ions (50 microM). Its kinetics were unchanged by substituting Ba for Ca, or in the presence of high concentrations of Ba. Both ICaT and ICaL exhibited reduced inactivation after high depolarizing prepulses. ICaT was found to be sensitive to dihydropyridines: 1 microM nifedipine decreased this current while 1 microM BAY K 8644 increased it; this occurred without significant variations in the steady-state inactivation curve. ICaT was more sensitive than ICaL to alpha 1-adrenergic and P2-purinergic stimulations, while ICaL was more sensitive to beta-adrenergic stimulation. Isoproterenol was still able to increase ICaT in the presence of high intracellular cAMP. Both currents were increased by 1 microM ouabain (although ICaL only transiently) and decreased by 10 microM ouabain. It is concluded that the two types of Ca channels can be observed in bullfrog atrial cells and that they are specifically altered by pharmacological agents and neuromediators. This may have implications for cardiac behavior.
J Gen Physiol 1992 Sep
PMID:Properties of the low threshold Ca current in single frog atrial cardiomyocytes. A comparison with the high threshold Ca current. 127 97

Using purified bacterially expressed herpes simplex virus type 1 ribonucleotide reductase large subunit (R1) and the proteolytic enzymes chymotrypsin and trypsin, we have generated stable N-terminal truncations. Chymotrypsin removes 246 amino acids from the amino terminus to produce a fragment (dN246R1) which retains full enzymic activity and affinity for the small subunit (R2). Treatment of R1 with trypsin produces a 120K protein and a cleavage at amino acid residue 305 to produce a fragment (dN305R1) which remains associated with a 33K N-terminal polypeptide. Although this 33K-dN305R1 complex retains full binding affinity for R2 its reductase activity is reduced by approximately 50%. Increasing the concentration of trypsin removes the 33K N-terminal polypeptide resulting in dN305R1 which, when bound to R2, has full ribonucleotide reductase activity. Like R1, dN246R1 and dN305R1 each exist as dimers showing that the first 305 amino acids of R1 are not necessary for dimer formation. These results indicate that, in structural studies of subunit interaction, dN246R1 or dN305R1 can be considered as suitable replacements for intact R1.
J Gen Virol 1992 Jan
PMID:The unique N terminus of the herpes simplex virus type 1 large subunit is not required for ribonucleotide reductase activity. 130 56

Soluble rhinovirus minor group binding activity was found to be shed into the medium upon incubation of HeLa cells at 37 degrees C. Although substantial amounts of this protein were released, no decrease of virus binding to the cell surface was seen. When the membrane-associated receptor was stripped from the cells with trypsin, virus binding was rapidly restored from an intracellular pool even in the absence of de novo protein synthesis. The release of this 85K virus-binding activity was inhibited by metal chelators such as EDTA, EGTA or 1,10-phenanthroline. The potential involvement of a Ca(2+)-dependent protease and/or a phospholipase in this process is discussed.
J Gen Virol 1992 Mar
PMID:Shedding of a rhinovirus minor group binding protein: evidence for a Ca(2+)-dependent process. 131 22

Torpedo electric organ has been used to study the binding of botulinum neurotoxin type A to pure cholinergic synaptosomes and presynaptic plasma membrane. 125I-labeled botulinum neurotoxin type A exhibits specific binding to cholinergic fractions. Two binding sites have been determined according to data analysis: a high affinity binding site (synaptosomes: Kd = 0.11 +/- 0.03 nM, Bmax = 50 +/- 10 fmol.mg prot-1; presynaptic plasma membrane: Kd = 0.2 +/- 0.05 nM, Bmax = 150 +/- 15 fmol.mg prot-1) and a low affinity binding site (synaptosomes: Kd approximately 26 nM, Bmax approximately 7.5 pmol.mg prot-1; presynaptic plasma membrane: Kd approximately 30 nM, Bmax approximately 52 pmol.mg prot-1). The binding of 125I-botulinum neurotoxin type A is decreased by previous treatment of synaptosomes by neuraminidase and trypsin, and by a preincubation with bovine brain gangliosides or antiserum raised against Torpedo presynaptic plasma membrane. When presynaptic plasma membranes are blotted to nitrocellulose sheet, either 125I-botulinum neurotoxin or botulinum toxin-gold complexes bind to a M(r) approximately 140,000 protein. Botulinum toxin-gold complexes have also been used to study the toxin internalization process into Torpedo synaptosomes. The images fit the three step sequence model in the pathway of botulinum neurotoxin poisoning.
J Neural Transm Gen Sect 1992
PMID:Binding of botulinum neurotoxin to pure cholinergic nerve terminals isolated from the electric organ of Torpedo. 133 17

Sendai virus mutants, KDe-21 and KDe-62, which had undergone multiple cycles of replication in Madin Darby canine kidney (MDCK) cells in the absence of exogenous proteases were isolated. The fusion (F) protein of the mutants regained proteolytic cleavability in MDCK cells and chick embryos, but the F protein remained non-cleavable in other cell lines. Unlike the F protein of wild-type (wt) virus, the mutant F was resistant to trypsin but was sensitive to elastase and, to a lesser extent, to chymotrypsin. Sequence analyses of the F gene and the F protein revealed an amino acid substitution at the cleavage site, Arg(116) to Ile, which conferred trypsin resistance and enhanced cleavability at Ile(116) by elastase and host proteases present in MDCK cells and in chicken embryos. In contrast to the pneumopathogenicity in mice of wt Sendai virus, the KDe mutants were non-pathogenic; cleavage activation of the F protein did not occur in the lungs and thereby infection was terminated after an initial cycle of replication.
J Gen Virol 1992 Jun
PMID:Changes in specific cleavability of the Sendai virus fusion protein: implications for pathogenicity in mice. 133 65

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). With respect to 1-MeAde production, the effect of GSS on follicle cells results in the receptor-mediated formation of cyclic AMP (cAMP). It has also been reported that methylation is involved in 1-MeAde production by GSS. This study was undertaken to determine whether cAMP is the agent responsible for mediating methylation in 1-MeAde biosynthesis by isolated follicle cells of the starfish Asterina pectinifera. Methionine and selenomethionine enhanced 1-MeAde production by GSS in follicle cells. These stimulatory effects were dependent on the GSS concentration. Production of 1-MeAde by GSS was inhibited by ethionine and selenoethionine, competitive inhibitors of methionine. Like GSS, 1-MeAde production induced by concanavalin A, trypsin, and 3-isobutyl-1-methylxanthine (IBMX), which stimulated cAMP accumulation in follicle cells, was influenced by methionine and its related compounds. In contrast, although 1-methyladenosine (1-MeAde-R) induced 1-MeAde production by follicle cells without increasing cAMP levels, methionine and its related compounds had no effect. Use of [methyl-14C]methionine showed that a radiolabel was incorporated into 1-MeAde during incubation with GSS and IBMX, but not with 1-MeAde-R. These results strongly suggest that cAMP plays an important role in the process of methylation during 1-MeAde biosynthesis induced by GSS.
Gen Comp Endocrinol 1992 Jul
PMID:Involvement of cyclic adenosine 3',5'-monophosphate in methylation during 1-methyladenine production by starfish ovarian follicle cells. 137 33

Two antigenic sites recognized by neutralizing monoclonal antibodies (MAbs) directed against the fusion (F) glycoprotein of human respiratory syncytial virus were mapped on the primary structure of the protein by (i) the identification of amino acid substitutions selected in antibody-escape mutants and (ii) the reactivity of synthetic peptides with MAbs. The first site contained several overlapping epitopes which were located within the trypsin-resistant amino-terminal third of the large F1 subunit. Only one of these epitopes was faithfully reproduced by a short synthetic peptide; the others might require specific local conformations to react with MAbs. The second antigenic site was located in a trypsin-sensitive domain of the F1 subunit towards the carboxy-terminal end of the cysteine-rich region. One of these epitopes was reproduced by synthetic peptides. In addition, mutagenized F protein with a substitution of serine for arginine at position 429 did not bind MAbs to the second site. These results are discussed in terms of F protein structure and the mechanisms of virus neutralization.
J Gen Virol 1992 Sep
PMID:Characterization of two antigenic sites recognized by neutralizing monoclonal antibodies directed against the fusion glycoprotein of human respiratory syncytial virus. 138 4

The oral spirochaete Treponema denticola ATCC 33520 was grown at a mean generation time of 10 h in anaerobic continuous culture in a serum- and carbohydrate-free medium at pH 7.0. The extracellular proteolytic activities of this spirochaete were then investigated by incubating washed cells with 68 2-naphthylamide derivatives of the Extended API System. Chymotrypsin-like, trypsin-like, elastase-like and iminopeptidase activities were demonstrated. The phenylalanine peptidase or chymotrypsin-like activity of T. denticola ATCC 33520, estimated with N-succinyl-L-phenylalanyl-L-leucyl-L-phenylalanine-thiobenzyl ester (SPLP) had a pH optimum at pH 8.5, a specific activity of 36.6 nmol min-1 (mg dry wt)-1 and was inhibited only slightly by HgCl2. The trypsin-like activity, estimated with benzoyl-DL-arginine-7-amido-4-methylcoumarin (BAMC), had a pH optimum at pH9, and a specific activity of 0.3 nmol min-1 (mg dry wt)-1; inhibition by HgCl2 indicated the involvement of active thiol groups. The activity should preferably be termed arginine peptidase activity, according to the carboxy-terminal amino acid of the test substrate. The extracellular proline peptidase activity, estimated with L-proline-7-amido-4-methylcoumarin. HBr (PRAMC), had an activity of 1.5 nmol min-1 (mg dry wt)-1, an optimum at pH 8.5 and the properties of a thiol protease. The main cell-bound and extracellular active peptidase activities of fast-growing cells of T. denticola ATCC 33520 are phenylalanine peptidase, proline peptidase, arginine peptidase and an oligopeptide-dependent alanine peptidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
J Gen Microbiol 1992 Sep
PMID:Cell-bound peptidase activities of Treponema denticola ATCC 33520 in continuous culture. 140 87

We investigated the possible involvement of oxidative mechanisms in the pathogenesis of influenza A/PR8/34 virus infection in mice. As a biochemical marker of oxidative stress, we determined the endogenous concentrations of the antioxidants glutathione and vitamins C and E in their reduced and oxidized forms in the lungs, liver and blood plasma of control and infected animals. Following intranasal infection with 8 to 10 LD50, influenza virus was detected in the lungs, but not in the plasma, liver or other organs. Infection resulted in a decrease in the total concentration of glutathione and vitamins C and E, whereas no relevant change in the ratio of oxidized to total concentration of antioxidants was observed. Changes in the concentration of hepatic antioxidants were significant in the early stages of the infection. The results suggest that hepatic alterations may be caused indirectly by mechanisms related to the host response to virus infection. The observed general decrease in the antioxidant buffering capacity may reduce the ability of tissues to protect against potential oxidative stress. Such stress can occur during bacterial superinfections, which are common in influenza, thereby rendering the host more susceptible to the pathogenic effects of such agents. In addition, reactive oxygen species produced in the lung may inactivate protease inhibitors, resulting in increased protease activity. Using an in vitro system consisting of alpha 1-antiprotease, trypsin and HOCl as the oxidant, we have shown that the infectivity of influenza viruses can be increased up to 10,000-fold by proteolytic cleavage of haemagglutinin, leading to activation of the fusogenic properties of this protein.
J Gen Virol 1992 Jan
PMID:Alterations in antioxidant defences in lung and liver of mice infected with influenza A virus. 153 Sep 63


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