Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superantigens are thought to make external contacts with major histocompatibility complex (MHC) class II molecules and with the V beta portion of a T cell antigen receptor (TCR), thereby stimulating entire families of T cells. The precise mapping of superantigen binding sites on class II molecules may provide valuable information on how TCR and MHC molecules interact. Two bacterial superantigens, staphylococcal enterotoxins A and E (SEA/SEE) bind well to most HLA-DR alleles, but poorly to HLA-DRw53. The sequences responsible for this binding were localized to the putative alpha helix of the DR beta chain by measuring toxin binding to a panel of chimeric class II molecules expressed on transfected cells. Binding of SEA/SEE to the DRw14 (Dw9) molecule suggested that the conserved histidine 81 in the beta chain of most DR molecules was important, whereas the tyrosine 81 in the DRw53 beta chain was detrimental for high-affinity binding. To prove this, reciprocal point mutations were introduced in the DR1 and DRw53 beta chains. Mutation of histidine 81 in the DR1 beta chain to tyrosine reduced SEA/SEE binding, but did not prevent recognition of two DR1-restricted peptides by six of eight antigen-specific T cell lines. Conversely, introduction to histidine at position 81 in the DRw53 beta chain restored normal levels of SEA/SEE binding. These data suggest that a binding site of SEA and SEE lies on the outer face of the beta chain alpha helix, pointing away from the antigen-binding groove.
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PMID:Identification of HLA-DR1 beta chain residues critical for binding staphylococcal enterotoxins A and E. 137 Jun 84

In order to study perfusion effects of different liver preservation methods on liver structure, porcine livers were perfused with either Bretschneider's HTK (Histidine Tryptophane Ketoglutarat) solution, Euro-Collins (EC) solution or University of Wisconsin solution (UW) according to the respective recommended protocols. Subsequently, together with a group of unprotected livers, all organs were examined by light and electron microscopy including computer assisted morphometry. The width of the space of Disse, the continuity of endothelial cells and the ultrastructure of the hepatocytes were not impaired after cold perfusion with any of the 3 solutions. However, we found considerable differences between the groups with respect to removal of blood cells from liver sinusoids. Livers flushed according to the HTK-protocol had the lowest residual blood cell content followed by the livers of the EC- and the UW-group. Centrilobular regions of the liver lobules were generally better washed free of blood than periportal zones. Computer assisted morphometry did not reveal any significant difference between the size of hepatocytes of EC-, UW- and HTK livers. Only the hepatocytes of normothermic control livers (biopsy samples) were 10% larger than hepatocytes of cold flushed groups. None of the protective perfusion protocols showed structural signs of perfusion injury.
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PMID:Morphological investigation of the porcine liver directly following preservation with Euro-Collins, University of Wisconsin and Bretschneider's HTK solution. 158 86

Neutral endopeptidase (EC 3.424.11, NEP) is a membrane-bound zinc-metallopeptidase. The substrate specificity and catalytic activity of NEP resemble those of thermolysin, a bacterial zinc-metalloprotease. Comparison of the primary structure of both enzymes suggests that several amino acids present in the active site of thermolysin are also found in NEP. Using site-directed mutagenesis of the cDNA encoding the NEP sequence, we have already shown that His residues 583 and 587 are two of the three zinc ligands. In order to identify the third zinc ligand, we have substituted Val or Asp for Glu616 or Glu646. Val616 NEP showed the same kinetic parameters as the non-mutated NEP. In contrast, the mutant Val646 NEP was almost completely devoid of catalytic activity and unable to bind the tritiated inhibitor [3H]N-[2(R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxypropyl]gl ycine, the binding of which is dependent on the presence of the zinc ion. Replacing Glu for Asp at position 646 conserved the negative charge, and the mutant enzyme exhibited the same Km value as the non-mutated enzyme, but kCat was decreased to less than 3% of the value of the non-mutated enzyme. When compared to the non-mutated enzyme Asp646 NEP showed a higher susceptibility to chelating agents, but bound the tritiated inhibitor with the same affinity. Taken together, these observations strongly suggest that Glu646 of NEP is the third zinc-coordinating residue and is equivalent to Glu166 in thermolysin.
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PMID:Identification of glutamic acid 646 as a zinc-coordinating residue in endopeptidase-24.11. 167 40

31P NMR spectroscopy was used to study the time course of changes in the concentration of high-energy metabolites and intracellular pH in the dog myocardium during hypothermic ischaemia at 9 degrees C in Bretschneider (HTK-B) and St. Thomas' Hospital (StTH) cardioplegic solutions. It was found that ATP and phosphocreatine degrade slowlier in HTK-B than in StTH, with phosphocreatine depletion occurring within 7.9 +/- 1.4 h in HTK-B and within 6.2 +/- 1.4 h in StTH. The values are virtually identical with the time intervals at which ATP concentration falls below the critical level (60% of initial ATP concentration). In agreement with biochemical analysis, a higher concentration of phosphomonoesters was noted until the 180th minute of ischaemia in HTK-B, a finding suggesting more rapid glycogen degradation in HTK-B. Even though HTK-B contains a high concentration of histidine buffer, higher values of intracellular pH were found during ischaemia in StTH. The effect of extracellular concentration of sodium ions on intracellular pH is discussed.
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PMID:The phosphate pool of isolated dog heart during global ischaemia: comparison of two cardioplegic solutions with 31P NMR spectroscopy. 181 21

Preservation of the lung is still one of the most challenging problems, because due to limited procurement time not all organs available can be used. The most common procurement technique is flush perfusion of the pulmonary artery system. Alternative methods in clinical use are either the autologous working heart-lung preparation or donor core-cooling (DCC). The own concept presented here, modified to the special demands of multi-organ-procurement, combines DCC and interstitial equilibration adapted to intracellular ion concentration. DCC is induced by extracorporeal circulation (ECC) using a transportable heart lung machine including a highly effective cooling system: cooling circuit based on two parallel heat exchangers with ice-water cooling produced by a high-pressure overflow of a low-temperature ice block (-40 degrees C). While cooling by ECC stepwise hemodilution is achieved by priming volume and incorporation of the cardioplegic solution (Bretschneider-HTK). The aim of equilibration is to lower the extracellular levels of sodium and calcium, and to increase the level of potassium. Additionally, the buffer capacity of donor blood is increased by the incorporated histidine-buffer system (alpha-stat). To avoid donor organ edema the time of ECC should be as short as possible. Using our system donor organ temperatures below 10 degrees C are reached within less than 30 min. In addition to ECC, lung surface cooling is achieved by external overflow with cold arterial blood (internal mammary artery). Besides lung preservation the main advantage of this concept is the profound precooling of all visceral organs before their individual flush perfusion.
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PMID:[The concept of lung and heart-lung preservation within the scope of multiple organ procurement]. 190 76

A series of renin inhibitors containing lactam-bridged P1-P1' dipeptide mimetics based on the ACHPA (4(S)-amino-5-cyclohexyl-3(S)-hydroxypentanoic acid) design was studied. The inhibitors were obtained by aldol addition of various lactams with N alpha-Boc-L-cyclohexylalaninal, followed by Boc group removal and acylation with Boc-Phe-His. The aldol diastereomer having the S configuration at the two newly generated stereogenic centers gave optimal enzyme inhibition. Potency was further enhanced in the gamma-lactam ring series by substitution with small hydrophobic groups to mimic the P1' side chain of the renin substrate. Thus, 2(S)-[(Boc-L-phenylalanyl-L-histidyl)amino]-3-cyclohexyl-1(S)-hydroxyl-1 - (1,5,5-trimethyl-2-oxopyrrolidin-3(S)-yl)propane (34) has an IC50 of 1.3 nM in the human plasma renin assay. A variety of substituents on the lactam nitrogen are tolerated and can be used to vary the physical properties of the inhibitor. By using a model of the human renin active site, the conformation of 34 in the enzyme-inhibitor complex is proposed. This modeled conformation is very similar to the solid-state conformation of 2(S)-[(Boc-L-phenylalanyl-L-histidyl)amino]-3-cyclohexyl-1(S)-hydroxyl- 1-(1-methyl-2-oxopyrrolidin-3(S)-yl)propane (36), the structure of which was determined by single-crystal X-ray diffraction analysis. The most potent ACH-PA-lactam renin inhibitors show good selectivity when assayed against other types of aspartic proteinases. By varying the lactam ring substituents, potent and selective inhibitors of cathepsin D and cathepsin E can be obtained.
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PMID:Renin inhibitors containing conformationally restricted P1-P1' dipeptide mimetics. 200 69

In order to evaluate the importance of glycogen for the hepatic tolerance to ischemia, livers of swine fed a glucose-potassium solution for premedication were perfused with either Bretschneider's HTK-solution (histidine-tryptophan-ketoglutarate) or with Euro-Collins-solution (EC) prior to subsequent ischemia at 25 and 5 degrees C. During ischemia, in regular intervals or continuously, energy rich phosphates, lactate, intrahepatic pH and the electrical impedance of liver tissue were determined. The results were compared with corresponding data from swine which had starved for 48 h. Corresponding to the higher glycogen content, energy supply during ischemia was markedly improved by the premedication. Despite high amounts of glucose in the EC-solution, energy supply after glucose-potassium premedication was no better with EC-solution than with HTK-solution. Moreover, glucose uptake led to concomitant cellular water uptake. Electrical impedance measurements during ischemia mirrored improved energetical protection by the glucose-potassium premedication.
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PMID:Glycogen effects on energy state and passive electric properties of liver during protection. 211 13

Endothelial cell damage caused by myocardial cardioplegic solutions (Bretschneider HTK and St. Thomas' Hospital No. 2) or renal and hepatic cold storage solutions (modified Collins and University of Wisconsin solution) was assessed in monolayer cultures of adult human venous endothelial cells at 4 degrees to 10 degrees C with phase-contrast microscopy. St. Thomas' Hospital solution caused the cells to contract, resulting in disruption of monolayer integrity and opening of intercellular gaps, and resulted in a 24-hour postexposure survival of 51.0% +/- 2.4%. Bretschneider HTK solution altered cellular morphology less and produced the best postexposure survival (80.2% +/- 2.6%; p less than 0.001). Although morphology was altered the least with University of Wisconsin solution, postexposure survival with this solution, which was similar to that with modified Collins solution, was superior to that with St. Thomas' (p less than 0.01) but inferior to that with Bretschneider HTK (p less than 0.05). The superior protection provided by Bretschneider HTK was due to its additives histidine, tryptophan, and KH-2-oxygluterate (p less than 0.005), and to its low chloride content (p less than 0.005). Furthermore, modifying St. Thomas' solution by decreasing its chloride content improved cell survival to 71.2% +/- 2.3% (p less than 0.001). Normothermic (37 degrees C) exposure to Bretschneider HTK, modified Collins, and University of Wisconsin solution was cytotoxic, whereas normothermic exposure to St. Thomas' cardioplegia was not. In conclusion, the preservation solution that is the least harmful to endothelial cells at hypothermia is Bretschneider HTK cardioplegic solution.
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PMID:Endothelial cell toxicity of solid-organ preservation solutions. 212 22

The effects of the cardioplegic solution HTK on membrane potential (EM) and intracellular K and Na activities (aiK, aiNa) were studied in sheep cardiac Purkinje fibres by means of conventional and ion-selective microelectrodes. HTK contains (mM): Na 15, K 10, Ca 0, Mg 4, histidine 180. (1) In control conditions EM was -74.3 +/- 3.3 mV (n = 25), aiK was 116.4 +/- 4.1 mM (n = 7) and aiNa was 8.2 +/- 1.4 mM (n = 15). (2) Exposure to HTK led to a depolarization to -59.7 +/- 3.6 mV (n = 25) which exceeded by about 5-7 mV that induced in a Tyrode solution of 10 mM K and in a modified HTK solution supplemented by 2 mM Ca (n = 6). (3) Addition of 0.5 mM barium eliminated the difference in the steady-state depolarization. (4) HTK superfusion increased aiK to 120.1 +/- 4.4 mM (n = 7) and decreased aiNa to 3.9 +/- 0.9 mM (n = 15). (5) The decrease in aiNa was insensitive to amiloride (1 mM) and to external alkalization but was slightly increased by addition of 2 mM calcium. (6) When the calcium in Tyrode solution was lowered from 2.0 mM to 0.05 mM, aiNa hardly decreased during subsequent exposure to unmodified HTK and it increased in the presence of 0.1 mM dihydroouabain. We propose the hypothesis (1) that the difference in membrane depolarization between HTK and a 10 mM K-Tyrode is caused by a decrease in K conductance by the HTK solution and (2) that the aiNa decline mainly results from a coupled Ca influx via Na-Ca exchange due to a delayed washout of external calcium.
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PMID:The cardioplegic solution HTK: effects on membrane potential, intracellular K+ and Na+ activities in sheep cardiac Purkinje fibres. 251 7

The common acute lymphoblastic leukemia antigen (CALLA) is a 749-amino acid type II integral membrane protein that has been identified recently as the neutral endopeptidase 24.11 [NEP (EC 3.4.24.11)]. Herein, we characterize the organization of the human CALLA/NEP gene and show that it spans more than 80 kilobases (kb) and is composed of 24 exons. Exons 1 and 2 encode 5' untranslated sequences; exon 3 [170 base pairs (bp)] encodes the initiation codon and transmembrane and cytoplasmic domain; 20 short exons (exons 4-23), ranging in size from 36 to 162 bp, encode most of the extracellular portion of the enzyme; and exon 24 (approximately 3400 bp) encodes the COOH-terminal 32 amino acids of the protein and contains the entire 3' untranslated region (UTR). Of note, the pentapeptide sequence (His-Glu-Ile-Thr-His) associated with metalloprotease zinc binding and substrate catalysis is encoded within a single exon (exon 19). Three types of CALLA/NEP cDNAs have been identified: these clones contain 5' UTR sequences differing from one another upstream of exon 3. These human 5' sequences are homologous to those found in rat brain and rabbit kidney NEP cDNAs. The three human CALLA cDNA types result from alternative splicing of exons 1, 2a, or 2b to the common exon 3. Moreover, exons 2a and 2b share the same 5' sequence but differ from each other by the use of two distinct donor splice sites 171 bp apart in the gene. The substantial conservation of 5' untranslated sequences among species and the existence of 5' alternative splicing suggest that CALLA gene expression may be differentially controlled in a tissue-specific and/or developmentally regulated fashion.
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PMID:Organization of the gene encoding common acute lymphoblastic leukemia antigen (neutral endopeptidase 24.11): multiple miniexons and separate 5' untranslated regions. 252 30


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