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)

1. Rat and guinea-pig lung tissues were incubated for 20 min at 37 degrees C in Krebs-Ringer phosphate buffer at pH 7.4, or in Tyrode-Tris buffer at pH 8.2, and the release of histamine produced by adding different concentrations of compound 48/80 to the incubation medium was determined.2. At pH 7.4, increasing concentrations of 48/80 increased the release of histamine from the rat lung, with a tendency towards a maximum. No release of histamine from guinea-pig lung was observed at this pH. At pH 8.2, histamine release occurred both from rat and guinea-pig lung, and was proportional to the logarithm of the concentration of compound 48/80.3. Histamine release from rat lung by 20 mug/ml. of 48/80 decreased when the pH was raised from 7.4 to 8.2; but the release caused by 1 mg/ml. of 48/80 increased both in rat and guinea-pig lung as the pH was raised.4. 2-4-Dinitrophenol (DNP) inhibited the release of histamine from rat lung by a concentration of 20 mug/ml. of 48/80; the inhibition was prevented by glucose. DNP did not affect histamine release from rat or guinea-pig lung by a concentration of 1 mg/ml. of 48/80 and enhanced the release when the pH was raised from 7.4 to 8.2.5. 1 mg/ml. of 48/80 did not inhibit the enhanced oxygen consumption produced by DNP in the isolated rat diaphragm.6. Iodoacetic acid (IAA) or a Ca/Mg-free medium inhibited the release of histamine by 20 mug/ml. of 48/80 from rat lung but not the release produced by 1 mg/ml. in either rat or guinea-pig lung.7. The degranulation of rat mesentery mast cells caused by 20 mug/ml. of compound 48/80 was inhibited by DNP. The degranulation evoked by 1 mg/ml. of 48/80 was also sensitive to this inhibitor; in this instance, however, the metachromatic staining reaction of the mesentery mast cells was greatly diminished.8. It is concluded that two processes of histamine release by compound 48/80 occur in rat lung. One, dependent on cell metabolism, involves, mast cell granule secretion. The other, independent of cell metabolism, seems to consist of a simple exchange reaction between histamine and compound 48/80, and this is the only one occurring in guinea-pig lung.
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PMID:Mechanisms of histamine release by compound 48-80. 418 29

Solvent isotope effects have been examined for the action of the zinc-containing metalloenzyme carboxypeptidase A on ester and peptide substrates. The kinetic parameters for the carboxypeptidase-catalyzed hydrolysis of an ester, O-(trans-cinnamoyl)-L-beta-phenyllactate, in 0.05 M Tris-DCl buffer containing 0.5 M NaCl at pD 8.07 and 25 degrees were compared with those obtained from measurements done in 0.05 M Tris-HCl buffer containing 0.5 M NaCl at pH 7.52 and 25 degrees . A (k(cat))(H2O)/(k(cat))(D2O) ratio of approximately 2 was obtained. The value of the Michaelis constant K(m) was unaffected by the change in solvent as was the inhibition constant, K(i), found for the product, L-beta-phenyllactate, which is a competitive inhibitor. These results indicate that a catalytic step involving general base catalysis is probably important in the carboxypeptidase-catalyzed hydrolysis of an ester. A similar set of experiments carried out on the peptide substrate, N-(N-benzoylglycyl)-L-phenylalanine gave ambiguous results. The role of the zinc ion in the catalytic action of carboxypeptidase A can be considered in the light of these findings.
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PMID:Effect of D2O on the carboxypeptidase-catalyzed hydrolysis of O-(trans-cinnamoyl)-L-beta-phenyllactate and N-(N-benzoylglycyl)-L-phenylalanine. 526 18

DL-2-Benzyl-3- formylpropanoic acid ( XIVb ) is a competitive inhibitor of carboxypeptidase A with an apparent Ki of 0.48 microM at pH 7.5 in 50 mM Tris buffer-0.5 M in sodium chloride with O-(trans-p- chlorocinnamoyl )-L-beta-phenyllactate as substrate. At pH 7.5 in deuterium oxide, DL-2-benzyl-3- formylpropanoic acid exists as an equilibrium mixture of 75% free aldehyde and 25% hydrated aldehyde. The species that binds to the enzyme may be either the free aldehyde or the hydrate. Therefore, the Ki of the species bound is significantly less than the observed Ki of 0.48 microM. The alcohol and dioxolane analogues of this aldehyde, DL-2-benzyl-4-hydroxybutanoic acid (XI) and 2-benzyl-4,4-(ethylenedioxy)butanoic acid ( XXVII ), are only weak inhibitors with Ki's of 0.54 mM and 2 mM, respectively. The ketone, (+/-)-3-(p- methoxybenzoyl )-2- benzylpropanoic acid [(+/-)-I; Sugimoto , T., & Kaiser, E. T. (1978) J. Am. Chem. Soc. 100, 7750-7751], was found to have a Ki of 180 microM, experimentally indistinguishable from that of the diastereomeric mixture of its alcohol analogue 2-benzyl-4-hydroxy-4-(p-methoxyphenyl)butanoic acid (III), Ki = 190 microM. The ketone (I) is not detectably hydrated (less than 2%) at pH 7.5 in deuterium oxide. These results suggest that the hydratable aldehyde DL-2-benzyl-3- formylpropanoic acid may mimic an intermediate resembling the transition state for amide hydrolysis by carboxypeptidase A while the nonhydratable ketone does not do so.
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PMID:Inhibition of carboxypeptidase A by aldehyde and ketone substrate analogues. 654 54

The crystal structure of the zinc-containing exopeptidase bovine carboxypeptidase A (CPA) has been refined to high resolution, based on a data set collected from a single crystal, incorporating new sequence information based on cloning of the bovine gene. In addition, new refined structures are available for the zinc-removed form of the enzyme, apo-CPA, as well as the mercury-replaced form, Hg-CPA. The native structure reveals that the zinc-bound water molecule does not appear to more loosely bound than the rest of the zinc ligands, at least when B-factor values are considered. Nor is there any evidence for a secondary location of this water molecule. The apo-enzyme structure does not show any density in the place of the removed zinc ion. The only significant change appears to be a chi2 rotation of one zinc histidine ligand to form an ion-pair interaction with a glutamic acid side chain. The structure of Hg-CPA reveals a solvent Tris molecule bound to the mercury cation, as well as an unidentified cation bound to Glu270. The location of this citation agrees with previous proposals for the binding side of inhibitory zinc. These observations may explain some of the differences in kinetics observed in metal- replaced CPA.
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PMID:Carboxypeptidase A: native, zinc-removed and mercury-replaced forms. 986 34


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