Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structures of the complexes of carboxypeptidase A with the amino acids D-phenylalanine and D-tyrosine are reported as determined by x-ray crystallographic methods to a resolution of 2.0 A. In each individual study one molecule of amino acids binds to the enzyme in the COOH-terminal hydrophobic pocket: the carboxylate of the bound ligand salt links with Arg-145, and the alpha-amino group salt links with Glu-270. The carboxylate of Glu-270 must break its hydrogen bond with the native zinc-bound water molecule in order to exploit the latter interaction. This result is in accord with spectroscopic studies which indicate that the binding of D or L amino acids (or analogues thereof) allows for more facile displacement of the metal-bound water by anions (Bicknell, R., Schaffer, A., Bertini, I., Luchinat, C., Vallee, B. L., and Auld, D. S. (1988) Biochemistry 27, 1050-1057). Additionally, we observe a significant movement of the zinc-bound water molecule (approximately 1 A) upon the binding of D-ligands. We propose that this unanticipated movement also contributes to anion sensitivity. The structural results of the current x-ray study correct predictions made in an early model building study regarding the binding of D-phenylalanine (Lipscomb, W. N., Hartsuck, J. A., Reeke, G. N., Jr., Quiocho, F. A., Bethge, P. H., Ludwig, M. L., Steitz, T. A., Muirhead, H., and Coppola, J. C. (1968) Brookhaven Symp. Biol. 21, 24-90).
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PMID:Binding of D-phenylalanine and D-tyrosine to carboxypeptidase A. 256 89

Structural fluctuations of the apoenzyme form of carboxypeptidase A (EC 3.4.12.2) have been evaluated on the basis of molecular dynamics. The Konnert-Hendrickson refined coordinates of 2437 non-hydrogen atoms of the 307 amino acid residues derived from the X-ray structure of the holoenzyme served as the molecular model together with 548 calculated polar hydrogen atoms and 25 buried solvent molecules. Molecular dynamics simulations were carried out at 277 K, and the averaged structural properties of the protein were evaluated for the terminal 20 picosecond portion of a 48 picosecond trajectory. The average atomic displacement from the initial X-ray structure was 2.49 A for all atoms and 1.79 A for C alpha atoms. The average root-mean-square (r.m.s.) fluctuation of all atoms was 0.67 A as compared to 0.54 A evaluated from the X-ray-defined temperature factors. Corresponding r.m.s. fluctuations for backbone atoms were 0.56 A by molecular dynamics and 0.49 A by X-ray. On the basis of these molecular dynamics studies of the isolated molecule, it is shown that amino acid residues corresponding to intermolecular contact sites of the crystalline enzyme are associated with high amplitude motion. All eight segments of alpha-helix and eight regions of beta-strand were well preserved except for unwinding of the five C-terminal residues of the alpha-helix 112-122 that form part of an intermolecular contact in the crystal. Four regions of beta-strand and one alpha-helix with residues adjacent to or in the active site constitute a core of constant secondary structure and are shown not to change in relative orientation to each other during the course of the trajectory. The absence of the zinc ion does not markedly influence the stereochemical relationships of active site residues in the dynamically averaged protein. The extent of motional fluctuations of each of the subsites of substrate recognition in the active site has been evaluated. Active site residues responsible for specificity of substrate binding or splitting of the scissile bond exhibit low simulated motion. In contrast, residues in more distal sites of substrate recognition exhibit markedly greater motional fluctuations. This differential extent of dynamical motion is related to structural requirements of substrate hydrolysis.
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PMID:Dynamical structure of carboxypeptidase A. 273 24

In an attempt to elucidate mechanisms underlying the irradiation-induced decrease in regional cerebral blood flow (rCBF) in primates, hippocampal and visual cortical blood flows of rhesus monkeys were measured by hydrogen clearance, before and after exposure to 100 Gy, whole-body, gamma irradiation. Systemic blood pressures were monitored simultaneously. Systemic arterial plasma histamine and neurotensin levels were determined preirradiation and postirradiation. Compared to control animals, the irradiated monkeys exhibited an abrupt decline in systemic blood pressure to 23% of the preirradiation level within 10 min postirradiation, falling to 12% by 60 min. A decrease in hippocampal blood flow to 32% of the preirradiation level was noted at 10 min postirradiation, followed by a slight recovery to 43% at 30 min and a decline to 23% by 60 min. The cortical blood flow for the same animals showed a steady decrease to 29% of the preirradiation levels by 60 min postirradiation. Animals given the mast cell stabilizer disodium cromoglycate and the antihistamines mepyramine and cimetidine before irradiation did not exhibit an abrupt decline in blood pressure but displayed a gradual decrease to a level 33% below preirradiation levels by 60 min postirradiation. Also, the treated, irradiated monkeys displayed rCBF values that were not significantly different from the nonirradiated controls. The plasma neurotensin levels in the irradiated animals, treated and untreated, indicated a nonsignificant postirradiation increase above control levels. However, the postirradiation plasma histamine levels in both irradiated groups showed an increase of approximately 1600% above the preirradiation levels and the postirradiation control levels. These findings implicate histamine in the postirradiation hypotension, but not necessarily in the direct responsibility for the decrease in regional cerebral blood flow seen immediately postirradiation in the primate.
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PMID:Effect of disodium cromoglycate (DSCG) and antihistamines on postirradiation cerebral blood flow and plasma levels of histamine and neurotensin. 289 22

It is proposed that proteins might activate specific atomic positions within bound substrates or co-factors by means of hydrogen-bond chains. As a result of a concerted proton (tautomeric) shift in the linked residues of the hydrogen-bond chain, which includes the bound molecule, a charge separation occurs. The charge thus generated at a specific atom of the bound molecule renders it nucleophilic or electrophilic, as the case may be, and hence 'activated' towards subsequent chemical events. To test the feasibility of the theory a survey of published X-ray diffraction determined structures was performed. A search was made for hydrogen-bond chains which emanate away from bound substrates, co-factors or metal ions in order to validate the existence of such structural arrangements. Secondly, an attempt was made to incorporate the proposed proton dynamics into the proteins' mechanisms of action. Examples in which these criteria were satisfied are carboxypeptidase A, carbonic anhydrase, haemoglobin, dihydrofolate reductase, glutathione reductase and p-hydroxybenzoate hydroxylase.
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PMID:Charge redistribution in proteins via linear hydrogen-bond chains. 309 99

Crystallographic analysis of the binding of mercaptoacetyl-L-valyl-L-tryptophan to thermolysin suggests that this inhibitor is hydrolyzed by the crystalline enzyme. The apparent product of hydrolysis, L-valyl-L-tryptophan (Val-Trp), occupies the S1'-S2' subsites of the active site, not the S1-S1' subsites as observed previously for the dipeptide L-alanyl-L-phenylalanine (Ala-Phe). The difference in binding of Val-Trp and Ala-Phe is consistent with the specificity requirements and preferences of thermolysin. The binding of Val-Trp illustrates the mode of interaction of one of the products of peptide hydrolysis. High resolution crystallographic refinement indicates that the valyl amino group makes three hydrogen bonds to the enzyme and to solvent and, in addition, is 2.8 A from the carboxylate of Glu-143. This is the first instance in which a direct interaction has been observed between Glu-143 and the scissile nitrogen. As such, the study directly supports the mechanism of action for thermolysin proposed by Hangauer et al. (Hangauer, D. G., Monzingo, A. F., and Matthews, B. W. (1984) Biochemistry 23, 5730-5741) and, by analogy, indirectly supports the similar mechanism proposed for carboxypeptidase A (Monzingo, A. F., and Matthews, B. W. (1984) Biochemistry 23, 5724-5729).
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PMID:The binding of L-valyl-L-tryptophan to crystalline thermolysin illustrates the mode of interaction of a product of peptide hydrolysis. 334 46

The effects of a new monochrome mast cell stabilizer (FPL 52694) on gastric secretion have been studied in healthy volunteers. When administered orally for 3 days, FPL 52694 consistently reduced nocturnal and pentagastrin-stimulated secretion of acid by about 50%. Meal-stimulated gastric secretion was not affected by the drug. Inhibition of the gastric secretory response to pentagastrin was not significant when single doses of the drug were administered either into the stomach or the duodenum, but administration of multiple doses resulted in significant inhibition. The drug does not inhibit gastric secretion by injuring the gastric mucosa, since the gastric mucosal barrier to back diffusion of hydrogen ions is not affected. We conclude that this mast cell stabilizer provides an interesting tool for studying aspects of the physiological control of gastric secretion and may have a therapeutic role in peptic ulceration.
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PMID:Effects of a mast cell stabiliser (FPL 52694) on human gastric secretion. 407 27

Various fixation and staining procedures have been examined in order to obtain optimal numbers and acceptable morphology of the mucosal mast cells and granular intraepithelial cells in the rat jejunum. For subsequent staining with Alcian Blue, the best fixation of the jejunum was obtained with a methanol-formaldehyde-acetic acid mixture. Specific staining of the granules of these cells has been obtained using Alcian Blue at pH 5.8, at which hydrogen ion concentration more cells stain than in the usual very acid conditions. Specificity is achieved by the use of magnesium chloride concentrations above the critical electrolyte concentrations for staining of protein and nucleic acid by Alcian Blue, and by the use of Safranin O as a competitive counterstain. The critical electrolyte concentration technique has also been applied to a comparative study of the glycosaminoglycan in the two cell types. Evidence is presented that the glycosaminoglycan in the granular intraepithelial cell has either a lower degree of sulphation or a lower molecular weight or both than the material in mucosal mast cells. This finding may support the possibility that the granular intraepithelial lymphocyte is a precursor of the mucosal mast cell.
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PMID:Fixation and staining of granules in mucosal mast cells and intraepithelial lymphocytes in the rat jejunum, with special reference to the relationship between the acid glycosaminoglycans in the two cell types. 616 Jan 26

The copper phthalocyanin dye astra blue has been used to stain differentially mast cells of the intestine; however; the procedure has not been used widely because of the difficulty in preparing and using the dye solution. Described here is a simple, reliable, and consistent method for selectively staining mast cells using a dye solution that may be prepared in any laboratory without the aid of sophisticated pH metering equipment. Astra blue is mixed with an alcoholic solution containing MgCl2-6H2O and the pH indicator pararosaniline hydrochloride. Concentrated hydrochloric acid is added dropwise, changing the dye mixture from purple to violet and then to blue. In this low range the weakly ionizing ethanol provides a more stable hydrogen ion concentration than the corresponding aqueous solutions used previously. Alcoholic acid fuchsin is a convenient counterstain, and this simple procedure then provides good contrast between the blue staining mast cell granules and the red tissue background.
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PMID:A simplified method for staining mast cells with astra blue. 616 2

Thiorphan, N-[(R,S)-3-mercapto-2-benzylpropanoyl]glycine is a highly potent inhibitor (Ki = 3.5 nM) of "enkephalinase," a metalloendopeptidase cleaving the Gly-Phe bond (positions 3 and 4) of enkephalins in brain tissue. In accordance with this property, thiorphan displays antinociceptive activity after systemic administration. However, thiorphan also inhibits to a lesser extent (Ki = 140 nM) the widely distributed angiotensin-converting enzyme, a carboxydipeptidase implicated in blood pressure regulation. Therefore, in view of an eventual clinical use of enkephalinase inhibitors, it was very important to develop fully specific compounds. Such derivatives were obtained taking into account that N-methylation of the ultimate amide bond of dipeptides strongly decreases enkephalinase affinity without affecting angiotension-converting enzyme recognition, whereas retro-inversion of the amide bond leads to the inverse effect. Thus, the retro-inverso dipeptide (R)-H2N-CH(CH2 phi)-NHCO-CH2-CO2H exhibits an inhibitory potency on enkephalinase (IC50 approximately equal to 12 muM) close to that of the natural dipeptide L-Phe-Gly (IC50 approximately equal to 3 muM). This result shows the topological analogy between the crucial components involved in enkephalinase recognition both in active dipeptides and structurally related retro-inverso isomers. Taking into account these observations, retro-thiorphan, (R,S)-HS-CH2-CH-(CH2 phi)-NHCO-CH2-COOH, was prepared. As compared to thiorphan, the retro isomer is 50% as potent (Ki = 6 nM) on enkephalinase but displays a drastic loss of potency on angiotension-converting enzyme (IC50 greater than 10,000 nM). This specificity was interpreted as a consequence of differences in the stereochemical constraints involving enzyme-inhibitor hydrogen bonding. This hypothesis is supported by reported crystallographic studies on related enzymes such as thermolysin and carboxypeptidase A. As expected, retro-thiorphan exhibits about the same analgesic potency as thiorphan on the hot plate and writhing tests in mice. Therefore, the topological concept of retro-inverso isomers could be extended to other enkephalinase inhibitors, allowing the design of potent and highly selective compounds occurring as new classes of analgesic and psychoactive agents.
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PMID:Complete differentiation between enkephalinase and angiotensin-converting enzyme inhibition by retro-thiorphan. 630 95

Heme-containing peroxidases have been demonstrated both biochemically and cytochemically in a variety of cells that either reside in the respiratory tract or circulate through it via the vasculature. The peroxidases in neutrophils and eosinophils have long been known to function in lung defense through their participation in an antimicrobial system involving hydrogen peroxide and chloride ions. Recent studies indicate that this system is also toxic to tumor cells and, as such, it may have a protective or mitigative effect on tumor formation in the lung. Eosinophil peroxidase may be involved in immediate hypersensitivity reactions in the lung because of its secretory effect on mast cells. Platelets contain peroxidases, but how they function is unknown. Whether peroxidase occurs in lymphocytes is controversial, but until more compelling evidence is presented they should be considered peroxidase-negative. A number of cells indigenous to the respiratory tract contain peroxidase activity, but there is considerable variability among species as to its presence and amount. When careful consideration is given to fixation and incubation conditions, peroxidase can be demonstrated cytochemically in the nuclear envelope and endoplasmic reticulum of some endothelial cells and type II cells of certain rodents, but its physiological role is speculative. The alveolar macrophages of most species possess little or no peroxidase activity apart from catalase which can function as a peroxidase under certain conditions. Mast cells in the respiratory tract contain peroxidase, but it is more easily demonstrated biochemically than cytochemically. The function of mast cell peroxidase is unknown, but two hypotheses worthy of investigation are its possible role in modulation of atopic allergic reactions and involvement in an antitumor defense mechanism similar to that of myeloperoxidase. Peroxidase is most abundant in the secretory cells of the tracheobronchial epithelium and glands where, in a number of species, it is synthesized and secreted as a component of mucus. Its possible contribution to lung defense is discussed in view of its morphologic similarity to the antibacterial peroxidase of milk and saliva. Because of the ease with which peroxidases can be demonstrated cytochemically, it is not surprising that morphologic information regarding their distribution in the respiratory tract has greatly exceeded insights into their functional significance. It is hoped that advancements in cell dissociation and culture, along with biochemical isolation and purification techniques, will lead to definitive conclusions concerning their physiologic roles in lung metabolism and defense.
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PMID:The distribution and function of peroxidases in the respiratory tract. 638 50


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