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)

Disulfide bonds in alpha 2-macroglobulin (alpha 2M) were reduced with the thioredoxin system from Escherichia coli. Under the conditions selected, 3.5-4.1 disulfide bonds were cleaved in each alpha 2M molecule, as determined by the consumption of NADPH during the reaction and by the incorporation of iodo[3H]acetate into the reaction product. This extent of disulfide bond reduction, approximately corresponding to that expected from specific cleavage of all four interchain disulfide bonds of the protein, coincided with the nearly complete dissociation of the intact alpha 2M molecule to a species migrating as an alpha 2M subunit in gel electrophoresis, under both denaturing and nondenaturing conditions. The dissociation was accompanied by only small changes of the spectroscopic properties of the subunits, which thus retain a near-native conformation. Reaction of isolated subunits with methylamine or trypsin led to the appearance of approximately 0.55 mol of thiol group/mol of subunits, indicating that the thio ester bonds are largely intact. Moreover, the rate of cleavage of these bonds by methylamine was similar to that in the whole alpha 2M molecule. Although the bait region was specifically cleaved by nonstoichiometric amounts of trypsin, the isolated subunits had minimal proteinase binding ability. Reaction of subunits with methylamine or trypsin produced changes of farultraviolet circular dichroism and near-ultraviolet absorption similar to those induced in the whole alpha 2M molecule, although in contrast with whole alpha 2M no fluorescence change was observed. The methylamine- or trypsin-treated subunits reassociated to a tetrameric species, migrating as the "fast" form of whole alpha 2M in gradient gel electrophoresis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Subunits of human alpha 2-macroglobulin produced by specific reduction of interchain disulfide bonds with thioredoxin. 245 51

The pre-steady-state reduction by NADPH of NADH:Q oxidoreductase, as present in submitochondrial particles, has been further investigated with the rapid-mixing, rapid-freezing technique. It was found that trypsin treatment, that had previously been used to inactivate the transhydrogenase activity (Bakker, P.T.A. and Albracht, S.P.J. (1986) Biochim. Biophys. Acta 850, 413-422), considerably affected the stability at pH 6.2 of the NAD(P)H oxidation activity of submitochondrial particles. Use of the inhibitor butadione circumvented this problem, thus allowing a more careful investigation of the kinetics at pH 6.2. In the presence of the inhibitor rotenone it was found that 50% of the Fe-S clusters 3 and all of the Fe-S clusters 2 and 4 could be reduced by NADPH within 30 ms at pH 6.2. The remainder of the Fe-S clusters 3 and all of the Fe-S clusters 1 were reduced slowly (complete reduction only after more than 60 s). It was concluded that these latter Fe-S clusters play no role in the NADPH oxidation activity. In the absence of rotenone at pH 6.2 only 50% of the Fe-S clusters 2-4 could be reduced within 30 ms, while Fe-S cluster 1 was again not reduced. This difference was attributed to the fast reoxidation of part of the Fe-S clusters 2 and 4 by ubiquinone. At pH 8.0, where the NADPH oxidation activity is almost zero, 50% of the Fe-S clusters 2-4 could still be reduced by NADPH within 30 ms, while Fe-S cluster 1 was not reduced. The presence of rotenone had no effect on this reduction. From these observations it is concluded that the Fe-S clusters 2 and 4, which were rapidly reduced by NADPH and reoxidised by ubiquinone at pH 6.2, could not be reduced by NADPH at 8.0. This provides an explanation why NADH:Q oxidoreductase was not able to oxidise NADPH at pH 8.0, while part of the Fe-S clusters were still rapidly reduced. As a working hypothesis a dimeric structure for NADH:Q oxidoreductase is proposed. One protomer (B) contains FMN and Fe-S clusters 1-4 in equal amounts; the other protomer (A) is identical except for the absence of Fe-S cluster 1. NADH is able to react with both protomers, while NADPH only reacts with protomer A. A pH-dependent electron transfer from protomer A to protomer B is proposed, which would allow the reduction of Fe-S clusters 2 and 4 of protomer B by NADPH at pH 6.2, which is required for NADPH:Q oxidoreductase activity.
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PMID:The pathway of electron transfer in NADH:Q oxidoreductase. 249 59

Cytochrome P-450BM-3 (P-450BM-3) from Bacillus megaterium incorporates both a P-450 and an NADPH:P-450 reductase in proteolytically separable domains of a single, 119-kDa polypeptide and functions as a fatty acid monooxygenase independently of any other protein. A 5-kilobase DNA fragment which contains the gene encoding P-450BM-3 was sequenced. A single continuous open reading frame starting at nucleotide 1541 of the 5-kilobase fragment correctly predicted the previously determined NH2-terminal protein sequences of the trypsin-generated P-450 and reductase domains and, in toto, predicted a mature polypeptide of 1,048-amino acid residues with Mr = 117,641. The trypsin site was found at arginine residue 471. The P-450 domain is most similar (about 25%) to the fatty acid omega-hydroxylases of P-450 family IV, while the reductase domain exhibits some 33% sequence similarity with the NADPH:P-450 reductases of mammalian liver. Both the P-450 and reductase domains of P-450BM-3 define new gene families but contain highly conserved segments which display as much as 50% sequence similarity with P-450s and reductases of eukaryotic origin. The mRNA for P-450BM-3 was found by S1 mapping to be 3,339 +/- 10 nucleotides in length. In the accompanying paper, two regions in the 1.5 kilobases 5' to the P-450BM-3 coding region have been implicated in the regulation of P-450BM-3 gene expression.
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PMID:Coding nucleotide, 5' regulatory, and deduced amino acid sequences of P-450BM-3, a single peptide cytochrome P-450:NADPH-P-450 reductase from Bacillus megaterium. 254 78

The HSITE program proposed in the previous paper was written to define putative ligand-point regions that could be found at protein surfaces. These regions would represent positions for hydrogen-bonding acceptor and donor atoms. In this paper the prediction of the location of these regions is compared with: (1) the position of the oxygen atoms of water molecules on the hydrated proteins myoglobin and plastocyanin; and (2) the position of hydrogen-bonded atoms in methotrexate and NADPH co-crystallized with dihydrofolate reductase, and in amidinophenyl-pyruvate co-crystallized with trypsin. The prediction of ligand-point regions is in agreement with the surveys of experimental data for water-molecule positions in protein crystals and with the positions of hydrogen-bonding atoms found in co-crystallized ligands.
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PMID:Automated site-directed drug design: the prediction and observation of ligand point positions at hydrogen-bonding regions on protein surfaces. 256 76

The vitamin E deficiency was studied for its effect on the activity of enzymes participating in metabolism of xenobiotics. Experiments with 54 rats have demonstrated that the maintenance of animals on the vitamin-E-deficient diet within 13-14 weeks decreases the activity of microsomal monooxygenases (demethylase and hydroxylase), NADH- and NADPH-reductases, aryl- and aliesterases in the liver and lungs, which is a result of disturbance of hydrophobic and polar interactions in microsomal membranes. Vitamin E deficiency makes the extent of solubilization of these enzymes higher under the influence of deoxycholate and trypsin and intensifies inactivation of these enzymes under the effect of urea. In the lungs and in the liver of the vitamin E deficient rats the content of reduced glutathione decreases as well as the activity of glutathione reductase, glutathione-S-transferase, aldehyde dehydrogenase, while the activity of gamma-glutamyltransferase increases; glutathione disulphide is accumulated.
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PMID:[The effect of vitamin E deficiency on enzyme activity and the status of the membrane fraction of rat liver microsomes]. 258 40

NADP+-specific glutamate dehydrogenase from Salmonella typhimurium, cloned and expressed in Escherichia coli, has been purified to homogeneity. The nucleotide sequence of S. typhimurium gdhA was determined and the amino acid sequence derived. The nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A-2',5'-DP) reacts irreversibly with the enzyme to yield a partially inactive enzyme. After about 60% loss of activity, no further inactivation is observed. The rate of inactivation exhibits a nonlinear dependence on 2-BDB-T epsilon A-2',5'-DP concentration with kmax = 0.160 min-1 and KI = 300 microM. Reaction of 200 microM 2-BDB-T epsilon A-2',5'-DP with glutamate dehydrogenase for 120 min results in the incorporation of 0.94 mol of reagent/mol of enzyme subunit. The coenzymes, NADPH and NADP+, completely protect the enzyme against inactivation by the reagent and decrease the reagent incorporation from 0.94 to 0.5 mol of reagent/mol enzyme subunit, while the substrate alpha-ketoglutarate offers only partial protection. These results indicate that 2-BDB-T epsilon A-2',5'-DP functions as an affinity label of the coenzyme binding site and that specific reaction occurs at only about 0.5 sites/enzyme subunit or 3 sites/hexamer. Glutamate dehydrogenase modified with 200 microM 2-BDB-T epsilon A-2',5'-DP in the absence and presence of coenzyme was reduced with NaB3H4, carboxymethylated, and digested with trypsin. Labeled peptides were purified by high performance liquid chromatography and characterized by gas phase sequencing. Two peptides modified by the reagent were isolated and identified as follows: Phe-Cys(CM)-Gln-Ala-Leu-Met-Thr-Glu-Leu-Tyr-Arg and Leu-Cys(CM)-Glu-Ile-Lys. These two peptides were located within the derived amino acid sequence as residues 146-156 and 282-286. In the presence of NADPH, which completely prevents inactivation, only peptide 146-156 was labeled. This result indicates that modification of the pentapeptide causes loss of activity. Glutamate 284 in this peptide is the probable reaction target and is located within the coenzyme binding site.
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PMID:Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate. 265 14

In vitro studies were performed to assess the ability of term human trophoblastic tissue to metabolize 25-hydroxyvitamin D3 (25OHD3) and to compare this metabolism to that occurring in porcine renal mitochondria and microsomes. Human trophoblastic homogenates, containing a NADPH-generating system, were able to produce 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] at a rate of 225 pg/mg protein.h, but did not produce detectable quantities (less than 20 pg/mg protein.h) of 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3]. Similarly, mitochondria and microsomes isolated from term human trophoblastic tissue produced 1,25-(OH)2D3 [249 +/- 156 and 199 +/- 82 (mean +/- SD) pg/mg protein.h, respectively] in the presence of an NADPH-generating system, but failed to produce detectable quantities (less than 200 pg/mg protein.h) of 24,25-(OH)2D3. The production of 1,25-(OH)2D3 from the trophoblastic mitochondria and microsomes could be increased by adding 140,000 x g trophoblastic cytosol to the subcellular incubation tubes. This treatment had no effect on the production of 24,25-(OH)2D3. The component(s) present in trophoblastic cytosol responsible for the increased 1,25-(OH)2D3 production by trophoblastic mitochondria and microsomes was shown to be heat labile, trypsin resistant, and less than 1000 mol wt in size. Comparing characteristics of the porcine renal 1 alpha- and 24R-hydroxylase systems with those of the human trophoblastic system revealed that 1) 1,2-dianilinoethane and EDTA totally blocked synthesis of 1,25-(OH)2D3 in trophoblastic mitochondria and microsomes, but had no effect on the synthesis of 1,25-(OH)2D3 by renal mitochondria; and 2) ketoconazole greatly inhibited the synthesis of 1,25-(OH)2D3 and 24,25-(OH)2D3 by renal mitochondria, but had no effect on the production of 1,25-(OH)2D3 by trophoblastic mitochondria or microsomes. Finally, production of 24,25-(OH)2D3 could not be demonstrated in trophoblastic homogenates, mitochondria, or microsomes, while the production of this compound was readily evident in renal mitochondria, but not microsomes. The results of this study question the existence of the 25-hydroxyvitamin D3-1 alpha- and 24R-hydroxylase systems in the trophoblastic portion of the human placenta. This study also suggests that 1,25-(OH)2D3 can be produced in vitro by a mechanism other than enzymatic 1 alpha-hydroxylation. The possibility exists that the mechanism involves the insertion of oxygen at the 1 position of 25-(OH)D3 by free radical chemistry.
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PMID:In vitro metabolism of 25-hydroxyvitamin D3 by human trophoblastic homogenates, mitochondria, and microsomes: lack of evidence for the presence of 25-hydroxyvitamin D3-1 alpha- and 24R-hydroxylases. 275 24

Purified cytochrome P-45011 beta from bovine adrenocortical mitochondria was successfully incorporated into the liposome membranes composed of phosphatidylcholine, phosphatidylethanolamine and cardiolipin at a molar ratio of 2:2:1. The incorporation of P-45011 beta into the liposome membranes was ascertained by the Ficoll density gradient centrifugation and the protein refractoriness to trypsin digestion. The prepared proteoliposomes containing P-45011 beta and phospholipid at a molar ratio of 1:3000 were unilamellar vesicles of about 40 nm in average diameter. The P-45011 beta embedded in the liposome membranes was found to be more stable than the detergent-solubilized form. The reconstituted system containing the P-45011 beta-proteoliposomes, adrenodoxin and NADPH-adrenodoxin reductase showed catalytic activities not only for the hydroxylation of 11-deoxycorticosterone at 11 beta- and 18-positions but also for its conversion into aldosterone with a turnover number of 2.3 nmol/min per nmol of P-45011 beta. A successive reaction without the intermediates leaving from the enzyme was suggested for the P-45011 beta-mediated conversion of 11-deoxycorticosterone to aldosterone following the result that the formation of aldosterone was linear with respect to time without the lag phase; this was confirmed by the result that radioactivity in aldosterone from 3H-labeled 11-deoxycorticosterone was scarcely decreased by the addition of unlabeled intermediates to the reactions system.
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PMID:Adrenal cytochrome P-45011 beta-proteoliposomes catalyzing aldosterone synthesis: preparation and characterization. 276 39

We have previously reported that addition of Ca2+ and phospholipid (PL) inhibits translation in hemin-containing reticulocyte lysates through activation of a eukaryotic protein synthesis initiation factor (eIF-2) kinase. The possibility that this activation was mediated by a Ca2+-PL-dependent protein kinase (protein kinase C, PKC) appeared unlikely by the observation that it was prevented or reversed by NADPH-generating systems. Nevertheless, reticulocyte lysates contain a potent PKC activity and we deemed it desirable to isolate this enzyme to answer unequivocally the question whether it does or does not activate eIF-2 alpha kinase. We have purified reticulocyte PKC to near homogeneity with Mr 95,500 as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme absolutely depended upon both Ca2+ and phosphatidylserine for activity on histone H1 or the beta-subunit of initiation factor eIF-2 and underwent autophosphorylation in a Ca2+- and PL-dependent manner. Mild treatment with trypsin yielded an Mr 82,000 polypeptide that still required Ca2+ and PL for activity. This Mr agrees with that reported for other PKCs, suggesting that these enzymes may undergo limited degradation during isolation. Further proteolytic treatment converted the reticulocyte enzyme into a Ca2+- and PL-dependent form, as is known for PKCs from other sources. The highly purified PKC had no effect on translation in hemin-supplemented reticulocyte lysates.
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PMID:Purification and properties of protein kinase C from rabbit reticulocyte lysates. 282 7

Experiments were performed to demonstrate the involvement of electron transport system in fatty acid elongation in rat brain microsomes. Mercuric chloride and p-chloromercuriphenylsulfonate, inhibitors on NADH-cytochrome b5 reductase, at 32 microM inhibited NADH-supported palmitoyl-CoA elongation to 30 and 60% of control activity, respectively, whereas NADPH-supported palmitoyl-CoA elongation was unaffected by these mercurials. An antibody to rat liver NADH-cytochrome b5 reductase inhibited brain microsomal NADH-cytochrome b5 reductase activity and NADH-dependent palmitoyl-CoA elongation. Treatment of brain microsomes with trypsin diminished the cytochrome b5 content; NADH- and NADPH-cytochrome c reductase activities were significantly decreased, but the decrease in NADH-cytochrome b5 reductase activity was relatively small. Whereas essentially no incorporation of malonyl-CoA into palmitoyl-CoA was observed with trypsin-treated microsomes, addition of detergent-solubilized cytochrome b5 resulted in a recovery of fatty acid elongation. These results indicate the presence of an electron transport system, NADH-NADH-cytochrome b5 reductase-cytochrome b5-fatty acid elongation, in brain microsomes.
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PMID:Palmitoyl-CoA elongation in brain microsomes: dependence on cytochrome b5 and NADH-cytochrome b5 reductase. 299 84


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