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)

Oxidative damage to bovine serum albumin (BSA) was induced by hydroxyl radical (HO.) generating systems of xanthine oxidase (XO) + EDTA-Fe3+ and ascorbate + EDTA-Fe3+. Formation of bityrosine and loss of tryptophan were observed in the ascorbate + EDTA-Fe3+ system and carbonyl formation was induced by both systems. Mannitol and ethanol very strongly inhibited the carbonyl and/or bityrosine formation, indicating that the oxidative damage to BSA was due to HO(.). The sulfhydryl (SH) groups of BSA were very sensitive to the XO + EDTA-Fe3+ but not to the ascorbate + EDTA-Fe3+ system. Catalase but not hydroxyl radical scavengers or superoxide dismutase strongly inhibited the loss of SH groups, indicating that H2O2 is involved in their oxidation. Fragmentation of BSA was observed during exposure to the XO + EDTA-Fe3+ and ascorbate + EDTA-Fe3+ systems and the products presented a broad band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Little formation of amine groups was observed in these systems, indicating that little peptide bond cleavage occurred. BSA exposed to the ascorbate + EDTA-Fe3+ system was more readily degraded by trypsin than that exposed to the XO + EDTA-Fe3+ system. Elastase degraded BSA exposed to the ascorbate + EDTA-Fe3+ system but not to the XO + EDTA-Fe3+ system.
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PMID:Oxidative damage to bovine serum albumin induced by hydroxyl radical generating systems of xanthine oxidase + EDTA-Fe3+ and ascorbate + EDTA-Fe3+. 133 12

Somatostatin 28 (S-28), originating in gastrointestinal cells, is secreted into the circulation and increases in humans after ingestion of a mixed meal. To evaluate the possibility that the increased levels of S-28 post cibum might modulate the release of enzymes and bicarbonate from the exocrine pancreas, S-28 was infused intravenously into healthy volunteers to levels seen after food intake. During S-28 infusion, the output of lipase, trypsin, amylase, and bicarbonate stimulated by either exogenous cholecystokinin octapeptide or endogenous signals from intraduodenal administration of tryptophan or a mixture of amino acids was significantly reduced. It is concluded that S-28 released from the gut during food intake modulates pancreatic exocrine function in humans.
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PMID:Evidence for hormonal inhibition of exocrine pancreatic function by somatostatin 28 in humans. 135 58

Efficient formation of the cpn60-rhodanese complex can be achieved by mixing unfolded rhodanese with excess cpn60 at low temperature. By employing these conditions, a stable and highly reactivatable complex is formed. The complex is not formed when native enzyme is used. Concentrations of NaCl, as high as 0.75 M, do not have any effect on the formation or disruption of the binary complex. cpn60-bound rhodanese contains an exposed hydrophobic surface, as detected by the binding of the fluorescent reporter, 1-anilinonaphthalene-8-sulfonic acid. The intrinsic fluorescence of cpn60-bound rhodanese reports that the average tryptophan is in an intermediate environment between that found in unfolded and native states. This form of rhodanese has an accessibility to quenching by acrylamide or iodide that is intermediate between the unfolded and native forms of the enzyme. Protease susceptibility studies show that rhodanese bound to cpn60 exhibits a trypsin digestion pattern similar to the native enzyme, although it is more rapidly proteolyzed. The results suggest that the conformation of cpn60-bound rhodanese resembles a native-like conformation, but with increased flexibility. Further, only intact rhodanese or enzyme lacking its N-terminal sequence can interact with cpn60 and form a stable binary complex. The protein fragment corresponding to the rhodanese N-terminal sequence did not form part of a stable complex with cpn60.
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PMID:Characterization of a stable, reactivatable complex between chaperonin 60 and mitochondrial rhodanese. 136 12

We have altered the amino acid at the center of the reactive site (methionine 73) of Streptomyces subtilisin inhibitor (SSI) by site-directed and cassette mutagenesis. Replacement by lysine or arginine resulted in trypsin inhibitory activity, replacement only by lysine gave inhibition of lysyl endopeptidase, and replacement by tyrosine or tryptophan resulted in inhibition of alpha-chymotrypsin. The four mutant SSIs retained their native activity against subtilisin BPN'. Thus by altering only one amino acid residue at the reactive site of SSI to the substrate specificity of the respective protease we could successfully change its inhibitory profile.
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PMID:Alteration of the specificity of the Streptomyces subtilisin inhibitor by gene engineering. 136 38

Decay accelerating factor (DAF) has 4 SCR (short consensus repeat) units. Each SCR unit consists of approx. 60 amino acids characterized by having four conserved cysteine residues and several other highly conserved residues which include proline, tryptophan, tyrosine/phenylalanine and glycine. To determine the disulfide-bonding pattern, we used the urine form of DAF. After thermolysin and trypsin digestion, we isolated seven disulfide-linked peptides by HPLC purification. Because all of the cysteine residues are disulfide-bonded, DAF should contain eight disulfide bonds. After subtilisin and trypsin digestion, we isolated the eighth disulfide-bonded peptides by HPLC purification. From sequence analyses of these peptides, we could identify all disulfide bonds in the 4 SCR units of DAF as being between the first and the third and between the second and the fourth half-cystines within each SCR unit.
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PMID:Complete determination of disulfide bonds localized within the short consensus repeat units of decay accelerating factor (CD55 antigen). 137 29

The channel-forming protein aerolysin is secreted as a protoxin which can be activated by proteolytic removal of a C-terminal peptide. The activation and subsequent oligomerization of aerolysin were studied using a variety of spectroscopic techniques. Mass spectrometric determination of the molecular weights of proaerolysin and aerolysin permitted identification of the sites at which the protoxin is processed by trypsin and chymotrypsin. The results of far- and near-UV circular dichroism measurements indicated that processing with trypsin does not lead to major changes in secondary or tertiary structure of the protein. An increase in tryptophan fluorescence intensity and a small red shift in the maximum emission wavelength of tryptophans could be observed, suggesting that there is a change in the environment of some of the tryptophans. There was also a dramatic increase in the binding of the hydrophobic fluorescent probe 1-anilino-8-naphthalenesulfonate during activation, leading us to conclude that a hydrophobic region in the protein is exposed by trypsin treatment. Using measurements of light scattering, various parameters influencing oligomerisation of trypsin-activated aerolysin were determined. Oligomerization rates were found to increase with the concentration of aerolysin, whereas they decreased with increasing ionic strength.
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PMID:Spectroscopic study of the activation and oligomerization of the channel-forming toxin aerolysin: identification of the site of proteolytic activation. 138 79

The Escherichia coli purine repressor, PurR, binds to a 16-bp operator sequence and coregulates the genes for de novo synthesis of purine and pyrimidine nucleotides, formation of a one-carbon unit for biosynthesis, and deamination of cytosine. We have characterized the purified repressor. Chemical cross-linking indicates that PurR is dimeric. Each subunit has an N-terminal domain of 52 amino acids for DNA binding and a C-terminal 289-residue domain for corepressor binding. Each domain was isolated after cleavage by trypsin. Sites for dimer formation are present within the corepressor binding domain. The corepressors hypoxanthine and guanine bind cooperatively to distinct sites in each subunit. Competition experiments indicate that binding of one purine abolishes cooperativity and decreases the affinity and the binding of the second corepressor. Binding of each corepressor results in a conformation change in the corepressor binding domain that was detected by intrinsic fluorescence of three tryptophan residues. These experiments characterize PurR as a complex allosteric regulatory protein.
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PMID:Structural characterization and corepressor binding of the Escherichia coli purine repressor. 140 Jan 70

We have developed and validated a new radioimmunoassay for cholecystokinin. In order to establish that the antiserum binds large and small forms of CCK to an equal extent, we used the microbial enzyme clostripain, which cleaves large forms of CCK yielding CCK 8. Cleavage by clostripain of synthetic and purified forms of CCK, and CCK extracted at from human jejunum and CCK in human plasma was found not to affect immunoactivity, indicating that the antiserum reacts similarly with all forms of CCK. There is controversy over whether intraduodenal trypsin inhibits release of CCK in man. We used our radioimmunoassay to investigate whether chymotrypsin, rather than trypsin, could be the major mediator of negative feedback control of CCK release. Six normal subjects received an intraduodenal infusion of L-phenylalanine and L-tryptophan on two occasions, with the addition of either 1 g/l bovine chymotrypsin or 1 g/l albumin. Plasma CCK concentrations rose in response to the amino acid infusion, but were not affected by the addition of chymotrypsin, indicating that this enzyme is not a mediator of CCK feedback regulation in man.
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PMID:Effect of chymotrypsin on human cholecystokinin release: use of clostripain in the validation of a new radioimmunoassay. 143 74

Fast skeletal myosins were isolated from carp acclimated to 10 and 30 degrees C, and their structural and enzymatic properties were compared. Myosins in 0.5 M KCl were subjected to limited proteolysis by using various proteases including alpha-chymotrypsin, trypsin, and papain, and different SDS-PAGE patterns were seen for the 10- and 30 degrees C-acclimated myosins in all cases. Myosin subfragment-1 (S1) prepared from the 10 degrees C-acclimated myosin by alpha-chymotryptic digestion in 0.12 M NaCl showed higher acto-S1 Mg(2+)-ATPase activity and lower thermostability than S1 from the warm-acclimated myosin. The peptide maps and ATP-induced spectral changes of tryptophan fluorescence also showed an obvious difference between the two types of S1. Temperature acclimation further caused changes in the rod region of myosin, since the apparent sizes of light meromyosin were different from each other for the two types of myosin. Myosin from carp acclimated to 20 degrees C showed intermediate properties between those of the 10- and 30 degrees C-acclimated myosins. Myosin isoforms might be expressed in a temperature-dependent manner to compensate for the effect of seasonal environmental temperature variation on swimming ability.
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PMID:Fast skeletal myosin isoforms in thermally acclimated carp. 153 74

Four distinct subspecies of the major insect lipoprotein, lipophorin, that range in overall lipid content from 20 to 51% of the particle mass, were isolated from the hemolymph or oocytes of the tobacco hornworm, Manduca sexta. Examination of these subspecies by electron microscopy revealed distinctive morphologies. Adult high density lipophorin (HDLp-A) was found to be an approximately spherical particle with a diameter of 15 +/- 1 nm, while HDLp-Wanderer 1 (W1), was more rectangular in shape and had a distinct cleft extending into the particle at one end. In the case of HDLp-Wanderer 2 (W2) the cleft was deeper and wider than that in HDLp-W1. In egg very high density lipophorin (VHDLp-E) the cleft was increased in size to the extent that the particle had an overall crescent-like conformation. Circular dichroism spectroscopy of the three lipophorin subspecies that contain only apolipophorin I and II revealed that only minor differences in the global protein secondary structure occur as the particle lipid content is decreased. The VHDLp-E apolipoproteins are an exception in that, while having the same alpha-helix content as HDLp-W1 and HDLp-W2, they contain less beta-structure and correspondingly more random coil. Limited digestion of the apolipoprotein components of the lipophorin subspecies with trypsin revealed that as the lipid content of the particles decreases the susceptibility of the apolipoprotein to proteolytic degradation increases. Likewise, tryptophan fluorescence quenching experiments demonstrated that the relative exposure of lipophorin apolipoprotein tryptophan residues also increases as the particle lipid content decreases.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of particle lipid content on the structure of insect lipophorins. 155 33


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