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)

Limited proteolysis of carboxypeptidase A from bovine pancreas with subtilisin Carlsberg generates a stable intermediate, carboxypeptidase S, whose esterase and peptidase activities are increased and decreased, respectively, under standard assay conditions. Carboxypeptidase S was isolated by affinity chromatography. Sequence analysis shows that it is cleaved solely at the Ala154-Gly155 bond. Its enzymatic properties were determined under stopped-flow conditions with Dns-Gly-Ala-Phe and its ester analogue Dns-Gly-Ala-OPhe. For both substrates, the Km values are increased 30-40-fold. The kcat value for peptide hydrolysis is virtually unaffected whereas that for ester hydrolysis is increased 10-fold. The magnitude of the Km effect is equivalent to a loss of 9 kJ/mol of binding energy and likely reflects a disruption of the network of hydrogen bonds that links Tyr-248 and Arg-145 to the backbone carbonyls of Ala-154 and Gly-155. The difference in kcat effects for the two substrate classes is related to differences in the chemical nature of the rate-determining step. Product release is rate determining for catalytic hydrolysis of ester substrates, and hence, the increase in kcat indicates that dissociation of products is facilitated as a result of the Ala154-Gly155 bond scission. The changes in enzymatic activity accompanying limited proteolysis are due to conformational alterations in the vicinity of the active center of the molecule. The affinity of a monoclonal antibody, mAb 100, directed toward the antigenic determinant located between residues 209 and 218 in carboxypeptidase A is diminished considerably for carboxypeptidase S.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Catalytic and conformational changes induced by limited subtilisin cleavage of bovine carboxypeptidase A. 169 55

The structure of the carboxypeptidase A complex with the inhibitor (S)-(+)-1-amino-2-phenylethylphosphonic acid has been determined at 0.23 nm resolution. The delta F map shows electron-density peaks both in the S1 and S'1 sites, where the inhibitor molecule can be modeled in two different orientations with approximate 50% occupancy. In the proposed model, the phosphonate group binds to the zinc ion in a monodentate fashion. Other anchoring groups for the inhibitor molecule are Arg127 (hydrogen bonds with the phosphonate oxygen atoms) and Glu270 (hydrogen bond with the amino group in one of the two orientations). A recent spectroscopic investigation of the complex between cobalt(II) carboxypeptidase A and (S)-(+)-1-amino-2-phenylethylphosphonic acid is essentially in agreement with our results.
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PMID:X-ray diffraction study of the interaction between carboxypeptidase A and (S)-(+)-1-amino-2-phenylethyl phosphonic acid. 173 Feb 23

The X-ray crystal structure of the carboxypeptidase A-L-benzylsuccinate complex has been refined at 2.0 A resolution to a final R-factor of 0.166. One molecule of the inhibitor binds to the enzyme active site. The terminal carboxylate forms a salt link with the guanidinium group of Arg145 and hydrogen bonds with Tyr248 and Asn144. The second carboxylate group binds to the zinc ion in an asymmetric bidentate fashion replacing the water molecule of the native structure. The zinc ion moves 0.5 A from its position in the native structure to accommodate the inhibitor binding. The overall stereochemistry around the zinc can be considered a distorted tetrahedron, although six atoms of the co-ordinated groups lie within 3.0 A from the zinc ion. The key for the strong inhibitory properties of L-benzylsuccinate can be found in its ability both to co-ordinate the zinc and to form a short carboxyl-carboxylate-type hydrogen bond (2.5 A) with Glu270.
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PMID:Crystal structure of the complex between carboxypeptidase A and the biproduct analog inhibitor L-benzylsuccinate at 2.0 A resolution. 173 64

Recently, Presta and Rose proposed that a necessary condition for helix formation is the presence of residues at the N- and C-termini (called NTBs and CTBs) whose side chains can form hydrogen bonds with the initial four amides and the last four carbonyls of the helix, which otherwise lack intrahelical hydrogen bonding partners. We have tested this hypothesis by conformational analysis by circular dichroism (CD) of a synthetic peptide corresponding to a region (171-188) of the protein carboxypeptidase A; in the protein, residues 174 to 186 are helical and are flanked by NTBs and CTBs. Since helix formation in this peptide may also be stabilized by electrostatic interactions, we have compared the helical content of the native peptide with that of several modified peptides designed to enable dissection of different contributions to helix stability. As expected, helix dipole interactions appear to contribute substantially, but we conclude that hydrogen bonding interactions as proposed by Presta and Rose also stabilize helix formation. To assist in comparison of different peptides, we have introduced two concentration-independent CD parameters which are sensitive probes of helix formation.
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PMID:Side chain-backbone hydrogen bonding contributes to helix stability in peptides derived from an alpha-helical region of carboxypeptidase A. 189 26

A 120ps non-inertial solvent (NIS) molecular dynamics (MD) trajectory of the potato carboxypeptidase A protein inhibitor (PCI) was calculated and analyzed. It is shown that, in spite of a very low content of regular secondary structure, the PCI fold has a large degree of stability, judged from the fairly good agreement between the average MD and X-ray structures. The N-terminal and C-terminal regions behave differently, both in their isoatomic positional shifts with respect to the X-ray structure, and in atomic fluctuation pattern. Positional shifts up to 9A are detected in the exposed N-terminal region as it folds back on the inhibitor's core. This large deviation is most likely caused by the absence of the receptor protein or by the lack of supporting solvent molecules. In contrast, the C-terminal region, which is the primary contact site with the enzyme, has an average structure similar to the X-ray conformation; this feature is probably due to a hydrogen bond network to the central core of PCI. The C-terminal tail shows larger fluctuations than the core. The secondary contact site retains its structure in this simulation. The results evidence an intrinsically stable PCI fold which favors a spatially well defined, fairly flexible, structuration of the primary and secondary contact sites that optimizes PCI's interaction with its target enzyme.
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PMID:Stability and fluctuations of the potato carboxypeptidase A protein inhibitor fold: a molecular dynamics study. 202 75

Incubation of oat root plasma membrane vesicles in the presence of ATP with trypsin or chymotrypsin increased the rate of ATP hydrolysis and ATP-dependent proton pumping by the plasma membrane H(+)-ATPase. Proton pumping was stimulated more than 200%, whereas ATP hydrolytic activity was stimulated about 30%. The Km (ATP) for both proton pumping and ATP hydrolysis was lowered from about 0.3 mM to below 0.1 mM. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of trypsin-treated plasma membranes revealed a decrease in a 100-kDa band and the appearance of a 93-kDa band. Western blot analysis using antibodies against the H(+)-ATPase showed that both of these bands represented the H(+)-ATPase and suggested that a 7-kDa segment was released. Extensive treatment with carboxypeptidase A also activated the H(+)-ATPase indicating that the 7-kDa segment originated from the C terminus.
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PMID:Proteolytic activation of the plant plasma membrane H(+)-ATPase by removal of a terminal segment. 214 84

Alveolar macrophages (AMs) and mast cells reside in the airway, and both have been demonstrated to contribute independently to allergic inflammatory responses through the generation of respiratory-burst metabolites and the release of biologically active mediators, respectively. Since mast cell granules (MCGs) contain mediators that could potentially interact with the AM respiratory burst, we investigated the effects of isolated MCGs on this important inflammatory pathway of the AM. MCGs and AMs were obtained by peritoneal and tracheoalveolar lavage, respectively, of Sprague-Dawley rats. First, the overall respiratory-burst activity was measured by luminal-enhanced chemiluminescence (CL), and second, the individual oxygen species contributing to CL (superoxide anion [O2-], hydrogen peroxide [H2O2], and hypochlorous acid) were measured. MCGs alone enhanced AM CL responses to an equivalent degree compared to zymosan-stimulated AMs. However, AMs preincubated with MCGs followed by zymosan stimulation significantly and synergistically enhanced the CL responses. This enhanced CL was not due to an increased production of O2-, H2O2, or hypochlorous acid; in fact, there were decreased measured amounts of O2- and H2O2 from zymosan-stimulated AMs in the presence of MCGs, most likely caused by the content of granules of superoxide dismutase and peroxidase, respectively. The lipoxygenase inhibitor, nordihydroguaiaretic acid, completely abolished the enhanced CL of AM preincubated with MCGs and subsequently stimulated by zymosan, but O2- production was not affected by nordihydroguaiaretic acid. Taken together, these results suggest that derivatives of arachidonic acid metabolism, most likely those of the lipoxygenase pathway, are responsible for the enhanced AM CL response observed in the presence of MCGs. Thus, mast cell-macrophage interactions may be important within the airway in enhancing the generation of mediators that contribute to tissue inflammation and bronchospasm.
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PMID:Mast cell granules modulate alveolar macrophage respiratory-burst activity and eicosanoid metabolism. 217 47

The gap junctions that electrically couple mammalian myocardial cells have high (12,000-17,000/micron2)surface densities of channel-containing elements (connexons), undulating surfaces, and approximately hexagonally arrayed connexons disposed in small domains rotated with respect to one another. Optical diffraction combined with image processing of negatively stained isolated rabbit heart gap junctions shows six protein subunits surrounding the cell-to-cell channel and suggestive (but not conclusive) evidence for protein connections between connexons. Biochemical studies indicate that the six identical relative molecular weight (Mr) 47,000 subunits of mammalian cardiac gap junctions differ from liver gap junctions in the presence of a covalently bound Mr 17,500 cytoplasmic surface component that can be visualized electron microscopically in thin-sectioned and freeze-etched hearts. The cytoplasmic surface component is susceptible to cleavage by an alkaline serine protease released from mast cell granules by high ionic strength solutions (0.6 M KI) used to extract myofibrils during gap junction purification. Interlocking of connexons from coupled cells in the gap involves hydrogen bonding between protein subunits of the connexons.
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PMID:Cell biology and protein composition of cardiac gap junctions. 240 91

Early transient incapacitation (ETI) is the complete cessation of performance during the first 30 min after radiation exposure and performance decrement (PD) is a reduction in performance at the same time. Supralethal doses of radiation have been shown to produce a marked decrease in regional cerebral blood flow in primates concurrent with hypotension and a dramatic release of mast cell histamine. In an attempt to elucidate mechanisms underlying the radiation-induced ETI/PD phenomenon and the postradiation decrease in cerebral blood flow, primates were exposed to 100 Gy (1 Gy = 100 rads), whole-body, gamma radiation. Pontine and cortical blood flows were measured by hydrogen clearance, before and after radiation exposure. Systemic blood pressures were determined simultaneously. Systemic arterial histamine levels were determined preradiation and postradiation. Data obtained indicated that radiated animals showed a decrease in blood flow of 63% in the motor cortex and 51% in the pons by 10 min postradiation. Regional cerebral blood flow of radiated animals showed a slight recovery 20 min postradiation, followed by a fall to the 10 min nadir by 60 min postradiation. Immediately, postradiation systemic blood pressure fell 67% and remained at that level for the remainder of the experiment. Histamine levels in the radiated animals increased a hundredfold 2 min postradiation. This study indicates that regional cerebral blood flow decreases postradiation with the development of hypotension and may be associated temporally with the postradiation release of histamine.
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PMID:Postradiation regional cerebral blood flow in primates. 242 23

Mast cells, when incubated in vitro with hydrogen peroxide (H2O2) and iodide, are cytotoxic to schistosomula of Schistosoma mansoni, as determined morphologically by dye exclusion, motility, and refractility and by transmission and scanning electron microscopy. When intact mast cells were incubated with schistosomula, mast cell degranulation with extracellular release of mast cell granules (MCG) was only observed in the presence of added H2O2 (10(-4) M). The secreted MCG, which contain small amounts of endogenous peroxidase activity, adhered to the surface of schistosomula. By 15 to 30 min, the mast cell-H2O2 system in the presence of iodide (10(-4) M) produced marked disruption of the tegumental and internal structures of the schistosomula. No helminthic damage was noted if any component of the incubation mixture (mast cells, H2O2 or iodide) was omitted. MCG could substitute for intact mast cells in the H2O2 and iodide-dependent cytotoxic system; MCG-mediated killing of schistosomula was inhibited by the hemeprotein inhibitor azide, suggesting that the cytotoxic reaction required endogenous peroxidase. The cytotoxicity was increased by eosinophil peroxidase bound to the MCG surface. These findings suggest a mechanism by which mast cells may contribute to the host cytotoxic response to helminths. H2O2 formed by nearby inflammatory cells may induce mast cell secretion, and the released MCG, through their endogenous peroxidase content (or bound eosinophil or neutrophil peroxidase), may react with H2O2 and a halide to form a system toxic to the adjacent helminth.
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PMID:Mast cell-mediated toxicity to schistosomula of Schistosoma mansoni: potentiation by exogenous peroxidase. 242 71


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