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)

A mass spectrometric method was developed to determine pH-dependent hydrogen-deuterium exchange at the C-2 position of the imidazole ring of histidine, after converting the amino acid to the methylthiohydantoin derivative. The amount of deuterium exchange in N-acetyl-histidine estimated by the present method was confirmed to be in good agreement with that determined by NMR spectrometry. N-Acetylhistidine was deuterated at various pH's. From the amount of deuterium exchange, a pseudo-first order rate constant (kpsi) was calculated. A pKa value of 7.2 for the amino acid was obtained from the relation between kpsi and pH. This method was applied to estimate the pKa value of beta-146 histidine in human hemoglobin. Human hemoglobin deuterated at various pH's was digested with carboxypeptidase A [EC 3.4.12.2] to release the beta-146 histidine. The amount of deuterium exchange in the isolated histidine was determined to obtain kpsi. From these measurements pKa values of 7.0 for the histidine in oxyhemoglobin and of 8.2 for that in deoxyhemoglobin were found at 36.5 degrees, respectively.
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PMID:Studies on the heterotropic interaction of hemoglobin. I. Mass spectrometric method for determination of the pKa of the beta-146 histidine residue in human hemoglobin. 1 48

Alpha-chymotrypsin (CT) was modified chemically and physically by the treatments with diisopropyl fluorophosphate, L-(1-tosylamide-2-phenyl) ethylchloromethylketone, hydrogen peroxide and heat. After these treatments, CT lost or decreased both the enzymic activity and ability of releasing histamine from rat mast cells. Ca++ was essential for histamine release by CT, while it enhanced only slightly the enzymic activity. Process of histamine release by CT could be separated into two stages: CT-dependent but not Ca++-dependent, and Ca++-dependent but not CT-dependent. The activated state of mast cells produced by CT decayed rapidly at 37 degrees C in the absence of Ca++, but these cells responded to Ca++ by adding CT once again, suggesting reconstitution of cell membrane structure affected by CT. Isoproterenol, epinephrine, prostaglandin E1, and dibutyryl-cyclic AMP (0.01-0.1 mM) did not inhibit release of histamine induced by CT. Neither theophylline (0.01-0.1 mM) alone nor the combinations of these cyclic AMP-active agents with theophylline inhibited the release of histamine. But, in the presence of papaverine (0.01-0.1 mM) a marked, dose-dependent inhibition was observed. These data suggest that 1) release of histamine by CT from rat mast cells is causally related to its hydrolytic activity, 2) this activity causes a reversible change on mast cell membrane which probably facilitates Ca++-influx through the cell membrane, and 3) there are subtle differences among CT, compound 48/80 and antigens concerning the effect of cyclic AMP-active agents in histamine-releasing mechanisms in mast cells.
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PMID:Mechanism of histamine release by alpha-chymotrypsin from isolated rat mast cells. 5 33

The source of the histamine released during damage to the gastric mucosa has been investigated in rats using perfused total gastric pouches. Two groups of rats were treated with either intraperitoneal normal saline or compound 48/80, and agent that produces mast cell degranulation, over a 5-day period. On the 5th day, total gastric pouches were prepared and connected to a perfusion circuit that enabled a 20-ml volume to be circulated through the pouches. The experiments consisted of three 30-min periods during which transmucosal potential difference was monitored and ionic (hydrogen and sodium) flux measured; standard acid solution was used in the first two periods and a taurocholate solution in the third. Sodium taurocholate produced a significant increase in ionic flux and fall in the potential difference, the magnitude of the changes being similar in the 48/80- and saline-treated groups. Histamine was released from the mucosa in significantly greater amounts during the taurocholate period, and the increase was similar in both groups of rats. Histological examination of the stomachs confirmed mast cell degranulation in the 48/80-treated groups. We conclude that the histamine released during mucosal damage is probably derived from the "nonmast cell pool" and that this histamine may play a role in mediating the mucosal damage.
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PMID:Effect of mast cell degranulation on gastric mucosal damage produced by sodium taurocholate in the rat. 7 16

Cobalt(III)bovine carbonic anhydrase B was prepared by the oxidation of the cobalt(II) enzyme with hydrogen peroxide and was purified by affinity chromatography. The oxidation reaction is inhibited by specific inhibitors of carbonic anhydrase. The inhibition is explained by the fact that the Co(II)-enzyme . inhibitor complex cannot be directly oxidized by hydrogen peroxide, but has to dissociate to give free Co(II) enzyme which is then oxidized. The Co(III) ion in Co(III) carbonic anhydrase cannot be directly substituted by zinc ions. It can be reduced by either dithionite or BH-4 ions to give, first, their complexes with the Co(II) enzyme, and upon their removal, a fully active Co(II) enzyme. Cyanide and azide bind to cobalt(III) carbonic anhydrase with similar rate constants of 0.060 +/- 0.005 and 0.070 +/- 0.007 M-1 S-1 respectively. These rates are faster than those found for Co(III) inorganic complexes. The Co(III) ion in both Co(III) carbonic anhydrase and Co(III) carboxypeptidase A was found to be diamagnetic, indicating a near octahedral symmetry.
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PMID:Kinetic and magnetic properties of cobalt(III) ion in the active site of carbonic anhydrase. 10 27

Catalytically inactive, exchange-inert Co(III)-carboxypeptidase A has been prepared by reaction of Co(II)-carboxypeptidase A with the active-site-directed oxidizing agent m-chloroperbenzoic acid. Co(III)-carboxypeptidase A, isolated by affinity gel filtration chromatography, has the same amino acid composition and molecular weight as the starting material and contains 0.95 g-atom/mol of cobalt and 0.01 g-atom/mol of zinc. Its electron paramagnetic resonance, circular dichroic, magnetic circular dichroic, and visible absorption spectra are consistent with those of octahedral Co(III) model complexes. Co(III)-caboxypeptidase A is essentially devoid of catalytic activity toward both peptide and ester substrates of the native enzyme, and stopped-flow fluorescence studies with dansylated substrates show that it binds peptides, but not esters. Furthermore, the protein does not react with either type of substrate to yield a single turnover. The implications of these findings to the mechanism of action of carboxypeptidase A are discussed in the light of the "metal-carbonyl" and "metal-hydroxide" hypotheses. Since Co(III)-carboxypeptidase A does not bind esters, inner-sphere coordination to the metal appears to be necessary for ester binding. All attempts to prepare Co(III)-carboxypeptidase A by treatment of Co(II)-carboxypeptidase A with hydrogen peroxide according to previously published procedures (Kang, E.P., Storm, C.B., & Carson, F.W. (1975) J. Am. Chem. Soc. 97, 6723) have been unsuccessful, and the present results do not confirm earlier reports that Co(III)-carboxypeptidase A exhibits esterase activity or that its activity is dependent on the method of preparation of the precursor Co(II)-carboxypeptidase A (Jones, M.M., Hunt, J.B., Storm, C.B., Evans, P.S., Carson, F.W. & Pauli, W.J. (1977) Biochem. Biophys. Res. Commun. 75, 253). These findings call for a reexamination of mechanistic conclusions based on the assumption that Co(III)-carboxypeptidase A is an active esterase.
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PMID:Enzymatically inactive, exchange-inert Co(III)-carboxypeptidase A: role of inner sphere coordination in peptide and ester catalysis. 21 Jul 89

The crystal structure of penicillopepsin, an extracellular acid protease isolated from the mold Penicillium janthinellum, has been determined at 2.8 A resolution by the method of multiple isomorphous replacement. The resulting electron density map computed from the native structure factor amplitudes and MIR phases has an overall mean figure of merit of 0.90. The molecule is decidedly nonspherical, with the majority of residues in beta-structure. There is an 18-stranded mixed beta-sheet which forms the structural core in the region of the active site. This site, identified by the covalent binding of two EPNP molecules to Asp-32 and Asp-215, is located in a deep groove which divides the molecule into two approximately equal lobes. Both aspartic acid residues in the active site are in intimate contact with one another and the carboxyl group of Asp-32 makes two other important hydrogen-bonded contacts: one with Ser-35 and the other with the main chain peptide bond between Thr-216 and Gly-217. A proposed mechanism for acid protease catalysis is similar in many aspects to that proposed for carboxypeptidase A. The electrophilic component which polarizes the substrate carbonyl bond in the acid proteases is the proton shared between the beta-carboxyl groups of Asp-32 and Asp-215. The beta-carboxyl group of Asp-32 removes a proton from a water molecule bound between this side chain and the substrate; the resultant OH- attacks the carbonyl carbon atom of the substrate molecule. The phenolic -OH group of Tyr-75 donates its proton to the amide nitrogen of the scissile bond of the substrate.
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PMID:Penicillopepsin: 2.8 A structure, active site conformation and mechanistic implications. 33 94

Hamster mast cells have been found to give strong peroxidatic reactions at pH 5, 7.5 and 10 when sections of skeletal muscle are incubated for 2.5 h in the dark at room temperature on semipermeable membranes covering a gelled incubation medium consisting of 0.01% hydrogen peroxide, 5.5mM diaminobenzidine and 1.36% agar dissolved in Universal buffer. The technique is very efficient: with it, all mast cells react in marked contrast to the negative reaction they usually give with conventional techniques. The peroxidatic reactions are abolished if tissues are perfused beforehand with either aminotriazole or KCN but not if these inhibitors are incorporated in the gelled incubation medium. This and other evidence suggests that the mast cell reactions are not due to either catalase or haemoglobin adsorbed onto mast cell granules from lysed red blood cells. Skeletal muscle fibres do not exhibit any visible peroxidase activity with the membrane technique.
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PMID:Endogenous peroxidase in mast cells localized with a semipermeable membrane technique. 66 84

The three-dimensional structure of (L(-)-2-carboxy-3-phenylpropyl) methylsulfodiimine in its complex with the zinc metalloenzyme carboxypeptidase A has been determined at 2.25-A resolution by x-ray crystallographic methods. This is the first example of a sulfodiimine-containing inhibitor binding to a zinc enzyme, and the structure of the enzyme-inhibitor complex reveals that the tetrahedral sulfodiimine group coordinates to the active site zinc ion in unidentate fashion. The zinc-coordinated nitrogen atom of the sulfodiimine group is also within hydrogen bonding distance to active site base Glu-270; presumably, the sulfodiimine is ionized and accepts a hydrogen bond from protonated Glu-270. The other sulfodiimine nitrogen accepts a hydrogen bond from Arg-127, and the inhibitor binds as a possible analogue of the tetrahedral transition state (or intermediate) in a promoted water pathway for peptide hydrolysis. The unidentate sulfodiimine-zinc binding mode observed in this enzyme-inhibitor complex is reminiscent of that observed in sulfonamide complexes with the zinc metalloenzyme carbonic anhydrase II, and the structural features of sulfodiimine- and sulfonamide-zinc interactions exhibit important similarities among recently determined structures of enzyme-inhibitor complexes: ionized nitrogens bind to zinc in each structure, and these nitrogens are engaged in hydrogen bond interactions with neighboring enzyme residues.
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PMID:Structural comparison of sulfodiimine and sulfonamide inhibitors in their complexes with zinc enzymes. 152 41

The molecular structures of three phosphorus-based peptide inhibitors of aspartyl proteinases complexed with penicillopepsin [1, Iva-L-Val-L-Val-StaPOEt [Iva = isovaleryl, StaP = the phosphinic acid analogue of statine [(S)-4-amino-(S)-3-hydroxy-6-methylheptanoic acid] (IvaVVStaPOEt)]; 2, Iva-L-Val-L-Val-L-LeuP-(O)Phe-OMe [LeuP = the phosphinic acid analogue of L-leucine; (O)Phe = L-3-phenyllactic acid; OMe = methyl ester] [Iva VVLP(O)FOMe]; and 3, Cbz-L-Ala-L-Ala-L-LeuP-(O)-Phe-OMe (Cbz = benzyloxycarbonyl) [CbzAALP(O)FOMe]] have been determined by X-ray crystallography and refined to crystallographic agreement factors, R ( = sigma parallel to F0 magnitude of - Fc parallel to/sigma magnitude of F0), of 0.132, 0.131, and 0.134, respectively. These inhibitors were designed to be structural mimics of the tetrahederal transition-state intermediate encountered during aspartic proteinase catalysis. They are potent inhibitors of penicillopepsin with Ki values of 1, 22 nM; 2, 2.8 nM; and 3, 1600 nM, respectively [Bartlett, P. A., Hanson, J. E., & Giannousis, P. P. (1990) J. Org. Chem. 55, 6268-6274]. All three of these phosphorus-based inhibitors bind virtually identically in the active site of penicillopepsin in a manner that closely approximates that expected for the transition state [James, M. N. G., Sielecki, A.R., Hayakawa, K., & Gelb, M. H. (1992) Biochemistry 31, 3872-3886]. The pro-S oxygen atom of the two phosphonate inhibitors and of the phosphinate group of the StaP inhibitor make very short contact distances (approximately 2.4 A) to the carboxyl oxygen atom, O delta 1, of Asp33 on penicillopepsin. We have interpreted this distance and the stereochemical environment of the carboxyl and phosphonate groups in terms of a hydrogen bond that most probably has a symmetric single-well potential energy function. The pro-R oxygen atom is the recipient of a hydrogen bond from the carboxyl group of Asp213. Thus, we are able to assign a neutral status to Asp213 and a partially negatively charged status to Asp33 with reasonable confidence. Similar very short hydrogen bonds involving the active site glutamic acid residues of thermolysin and carboxypeptidase A and the pro-R oxygen of bound phosphonate inhibitors have been reported [Holden, H. M., Tronrud, D. E., Monzingo, A. F., Weaver, L. H., & Matthews, B. W. (1987) Biochemistry 26, 8542-8553; Kim, H., & Lipscomb, W. N. (1991) Biochemistry 30, 8171-8180].(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Crystallographic analysis of transition-state mimics bound to penicillopepsin: phosphorus-containing peptide analogues. 160 44

We functionally characterized human skin mast cell carboxypeptidase A (MC-CPA), and explored its evolutionary relationship to other carboxypeptidases to understand further the structural basis for the substrate preferences of this enzyme. Purified human skin MC-CPA displayed more activity than did bovine pancreatic carboxypeptidase A (CPA) against carboxyl-terminal leucine residues, about equal activity with phenylalanine and tyrosine residues, and no activity with tryptophan or alanine. To correlate kinetic data with structure, we isolated and sequenced a cDNA encoding MC-CPA from human skin, and directly sequenced 30% of the purified protein. These sequences agreed with that of human lung MC-CPA, and further support the evidence for a single MC-CPA gene in humans. Four amino acid replacements, resulting in a net positive change in non-hydrogen atoms in the S1' subsite of MC-CPA, were associated with less alteration in substrate specificity, relative to bovine CPA, than might be expected from studies using rat CPA1 and CPA2. We noted two consensus N-linked glycosylation sites in human MC-CPA that are not found in rat and mouse MC-CPA, or in bovine CPA; that at least one of these sites is glycosylated in vivo was verified by N-glycosidase F treatment, lentil lectin binding, and Concanavalin A-Sepharose chromatography. Evolutionary trees constructed from the known carboxypeptidase sequences suggested that MC-CPA most likely evolved from a carboxypeptidase B-like enzyme, independent of the pancreatic CPA. Thus, in the carboxypeptidase gene family, MC-CPA displays a unique genealogy and several amino acid replacements in its S1' binding pocket that result in substrate specificity quite similar to bovine CPA.
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PMID:Human skin mast cell carboxypeptidase: functional characterization, cDNA cloning, and genealogy. 162 26


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