Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.16.2 (PCP)
3,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously demonstrated in permeabilized rat pancreatic acini that the existence of two affinity states of the pancreatic cholecystokinin (CCK) receptor seen in intact cells depends on the presence of ATP. In the present study, we demonstrate that this effect of ATP is mediated by the enzyme nucleoside diphosphate kinase (NDPK). Northern blot hybridization analysis demonstrated NDPK mRNA in pancreas. Furthermore, pancreatic membranes possessed NDPK activity, which transferred high-energy phosphate groups to [8-3H]GDP. This enzyme also utilized UTP and ITP as a source of gamma-phosphate for GTP formation while guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) was formed in the presence of adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S). However, adenylyl (beta, gamma-methylene)-diphosphate (AMP-PCP) did not serve as a substrate for NDPK. Analysis of 125I-Bolton-Hunter-labeled CCK octapeptide ([125I]BH-CCK-8) binding data in the absence of nucleotides was consistent with a single affinity state with dissociation constant (Kd) equal to 80 pM and maximal binding equal to 50.8 fmol/mg. ATP, UTP, ITP, ATP gamma S, and GTP gamma S all induced two CCK binding affinity states, which in the presence of 1 mM ATP were Kd = 74 pM for high-affinity sites and Kd = 4.3 nM for low-affinity sites: AMP-PCP did not induce two affinity states. GDP at 10 microM had no effect on CCK binding but potentiated the effect of ATP. GTP gamma S, in addition to inducing high- and low-affinity states, also elicited a significant concentration-dependent reduction in the total number of measurable CCK receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Nucleoside diphosphate kinase associated with rat pancreatic membranes regulates CCK receptor affinity. 797 49

The effect of a keto-derivative of cholesterol, namely, 6-ketocholestanol (5 alpha-cholestan-3 beta-ol-6-one; kCh) on the uncoupling of oxidation and phosphorylation by various uncouplers was studied in rat heart mitochondria. kCh was found to completely abolish the uncoupling effect (the increase in the respiration rate under the respiratory control conditions and the decrease in the membrane potential) caused of FCCP, CCCP and SF6847 and partially by TTFB at low concentrations of uncouplers. It was without effect on the uncoupling by PCP, DNP and palmitate. Carboxyatractylate, a specific inhibitor of the ADP/ATP-antiporter, was shown to almost completely abolish the uncoupling induced by palmitate and partially by low concentration of TTFB, PCP and DNP. Effects of high concentrations of all these uncouplers as well as of any concentrations of gramicidin proved to be kCh- and carboxyatractilate-insensitive. The data are discussed in terms of the hypothesis on the protein-mediated mechanism of the protonophorous uncoupling.
...
PMID:6-ketocholestanol abolishes the effect of the most potent uncouplers of oxidative phosphorylation in mitochondria. 798 94

Isolated pancreatic islets from rats and humans express a plasmalogen-preferring ATP-stimulatable, Ca(2+)-independent phospholipase A2 (ASCI-PLA2) enzyme which participates in the glucose-stimulated hydrolysis of arachidonate from membrane phospholipids and in insulin secretion. Here we report that clonal insulin-secreting HIT beta-cells contain substantial amounts of endogenous plasmalogens and express a similar ASCI-PLA2 activity with the following properties: (1) Enzymatic activity as well as glucose-induced eicosanoid release and insulin secretion are inhibited by a mechanism-based suicide substrate directed towards ASCI-PLA2. (2) HIT cell ASCI-PLA2 is selectively activated and protected against thermal denaturation by ATP. (3) The magnitude of ASCI-PLA2 activation by the nonhydrolyzable ATP analog AMP-PCP is similar to that by ATP. (4) The ATP concentrations required to activate ASCI-PLA2 fall within physiologic ranges in the presence of Mg2+. (5) ADP induces a concentration-dependent attenuation of the activation of ASCI-PLA2 by ATP. HIT cell ASCI-PLA2 exhibited an apparent isoelectric point of 7.5 on chromatofocusing analysis and was quantitatively adsorbed to an ATP-agarose matrix and selectively desorbed from this column by ATP. Mono-Q anion-exchange analysis of the active ATP-agarose eluant yielded a peak of ASCI-PLA2 activity associated with a single protein band with an apparent molecular mass of 40 kDa. Similar chromatographic behavior of the rat pancreatic islet ASCI-PLA2 activity was observed during sequential ATP-agarose and Mono-Q anion-exchange steps. These results indicate that HIT cells express an ASCI-PLA2 similar to the analogous islet enzyme and suggest that expression of this enzyme and of its preferred plasmalogen substrates may be a general property of insulin-secreting beta-cells.
...
PMID:Characterization of an ATP-stimulatable Ca(2+)-independent phospholipase A2 from clonal insulin-secreting HIT cells and rat pancreatic islets: a possible molecular component of the beta-cell fuel sensor. 800 9

3H-labeled 9-methyl-7-bromoeudistomin D ([3H]MBED), a powerful caffeine-like Ca2+ releaser, binds to the caffeine binding site of terminal cisternae (TC) of skeletal muscle sarcoplasmic reticulum (SR) (Fang, Y-I., Adachi, M., Kobayashi, J., and Ohizumi, Y. (1993). J. Biol. Chem. 268, 18622-18625.) and activates Ca(2+)-induced Ca2+ release (CICR). [3H]MBED, however, bound to rabbit hepatic microsomes with a comparable affinity (Kd = 50 nM) and with a more than 30-fold greater receptor density (Bmax = 350 pmol/mg of protein), compared with those in SR. Caffeine (0.1-10 mM) caused a concentration dependent inhibition of [3H]MBED binding to hepatic microsomes with the IC50 value of 0.3 mM. The mode of inhibition by caffeine was allosteric, indicating that the binding site of the ligand is distinct from but related to that of caffeine. Procaine (1-10 mM), a representative inhibitor of CICR, which suppresses [3H]MBED binding to TC-SR, inhibited ligand binding to hepatic microsomes only slightly. Moreover, ligand binding to the hepatic binding site was not affected by adenosine 5'-(beta, gamma-methylene) triphosphate (AMP-PCP) (10-100 microM), which is an activator of CICR and potentiates [3H]MBED binding to TC-SR. Inhibitors of [3H]MBED binding to liver microsomes other than caffeine were nucleotides such as ADP, ATP, GTP, UTP (1 mM), while CTP, cAMP, AMP, adenosine (1 mM), ryanodine (0.1-100 mM) and inositol 1,4,5-trisphosphate (1 microM) were not effective. These features of the hepatic microsomal [3H]MBED binding site distinguish it from that of skeletal muscle SR. [3H]MBED, which binds to the different sites which are both sensitive to caffeine, is useful as a probe to investigate the actions of caffeine at the molecular level.
...
PMID:The specific binding site of 9-[3H]methyl-7-bromoeudistomin D, a caffeine-like Ca2+ releaser, in liver microsomes in distinct from that in skeletal sarcoplasmic reticulum. 801 Nov 74

Activation of rat basophilic leukaemia cells (RBL-2H3) leads to the secretion of allergic and inflammatory mediators. These cells can be permeabilized, yet still retain their ability to secrete in response to antigen. Secretion can also be induced in permeabilized cells by the addition of the ATP analogue, ATP gamma S [adenosine-5'-O-(3-thiotriphosphate)], which is relatively resistant to phosphatase activity. ATP gamma S-induced secretion (35-50% of total amine) is temperature and concentration-dependent. Calcium enhances secretion, but unlike antigen-induced secretion, it does occur in the absence of calcium and without the requirement for inositol phospholipid hydrolysis. Other ATP analogues induced secretion in the rank order AMP-PNP > or = ATP gamma S >>> AMP-PCP > ATP alpha S = ATP [AMP-PNP, adenylyl-imidodiphosphate; AMP-PCP, adenylyl (beta,gamma-methylene)-diphosphonate; ATP alpha S, adenosine-5'-O-(1-thiotriphosphate)]. At equimolar concentrations, ATP inhibits ATP gamma S-induced secretion by 50%, but prolonged incubation in the presence of ATP gamma S surmounts the ATP inhibition. ADP is nearly as effective an inhibitor, but GTP and ITP are ineffective. It is likely that secretion occurs through attachment at an ATP-binding site, effectively blocking the action of a phosphatase, active later in the normal secretory pathway.
...
PMID:Calcium-independent secretion by ATP gamma S from a permeabilized rat basophilic leukaemia cell line (RBL-2H3). 808 86

The relaxant action of adenine nucleotides was studied in isolated rabbit trachealis to assess the presence of P2-purinoceptors in the airways, their cellular location, and pharmacologic properties. Strips of tracheal smooth muscle with intact epithelium were incubated in tissue baths and contracted with 1 microM acetylcholine. Over a dose range of 0.1 microM to 1 mM, ATP and ADP were significantly more potent than adenosine in relaxing tracheal smooth muscle. Significant relaxations were also elicited by AMP-PCP, AMP-CPP, and AMP-PNP, three ATP analogs stable to enzymatic hydrolysis to adenosine. In the absence of acetylcholine, neither ATP nor AMP-CPP exerted any contractile effect on the tracheal strips. In tissues selectively denuded of epithelium, ATP-, ADP-, and AMP-PCP-induced relaxations were markedly reduced. ATP-induced relaxation was also inhibited by the P2y-purinoceptor antagonist Reactive Blue 2 (RB2) (50 to 300 microM) and partially reduced by the cyclooxygenase inhibitor indomethacin (10 microM), whereas adenosine-induced relaxation was not significantly affected by these agents. These results suggest that ATP can induce smooth muscle relaxation in acetylcholine-contracted tracheal strips through a distinct P2-purinoceptor. This receptor appears to be located on the epithelium where its relaxant effect is mediated in part by release of one or more cyclooxygenase products. Additional relaxation at high ATP concentrations may occur through enzymatic hydrolysis of ATP to adenosine and interaction at P1-purinoceptors.
...
PMID:Relaxation of rabbit tracheal smooth muscle by adenine nucleotides: mediation by P2-purinoceptors. 811 Apr 78

The structure of Ca(2+)-ATPase has been studied by electron microscopy of two different crystal forms: one tubular form induced by vanadate in native sarcoplasmic reticulum (SR) membranes and another multilamellar form grown from detergent-solubilized SR. To determine the conformation of Ca(2+)-ATPase within each crystal form, the respective effects of Ca2+, thapsigargin, adenosine 5'-(beta, gamma-methylene)triphosphate) (AMP-PCP), and chromium(III) (Cr-ATP) on crystallization have been studied. Vanadate-induced tubes were prevented from forming by micromolar Ca2+, but if preformed in the absence of Ca2_, millimolar Ca2+ was required to disrupt these crystals. Thapsigargin promoted tube formation even in the presence of 10 mM Ca2+. Neither AMP-PCP nor Cr-ATP prevented tube formation, and the Ca2+ sensitivity of tube formation from Cr-ATP-inhibited SR was identical to controls. Multilamellar crystals required at least 0.2 mM Ca2+ and were prevented from forming by thapsigargin, AMP-PCP, or Cr-ATP. It is concluded that helical tubes are composed of the Ca(2+)-free, dephosphorylated conformation (E), and the nucleotide-bound conformation (E-ATP) is also tolerated. In contrast, multilamellar crystals are composed of the Ca(2+)-bound conformation (E.Ca2) and do not tolerate nucleotide binding. Thus, comparison of structures obtained from the two crystal forms should reveal physiologically relevant conformational differences.
...
PMID:Conformation of Ca(2+)-ATPase in two crystal forms. Effects of Ca2+, thapsigargin, adenosine 5'-(beta, gamma-methylene)triphosphate), and chromium(III)-ATP on crystallization. 815 94

The hepatocyte has an organic anion transport system that recognizes compounds such as bilirubin and sulfobromophthalein. These anions circulate bound tightly to albumin from which they are extracted rapidly by hepatocytes by an electroneutral process that requires extracellular inorganic anions such as Cl- for activity. Transport activity is reduced by depletion of intracellular ATP, but whether ATP interacts directly with this transporter is not known. In this study, the influence of extracellular ATP on the hepatocyte organic anion transport mechanism has been characterized. In the presence of 2.5 mM Ca2+ and 2 mM Mg2+, initial uptake of [35S]sulfobromophthalein was reduced by 50% at 1 mM ATP. In the absence of divalent cations sensitivity to ATP was 10-fold greater. Other nucleotides including UTP, CTP, GTP, ADP, AMP, and AMP-PCP (adenosine 5'-(beta,gamma-methylene)triphosphate) were inactive. Decreased transport activity was rapidly reversible, was non-competitive with respect to ATP, did not require ATP hydrolysis, and did not correlate with P2y purinergic receptor activity. Differential activity of ATP on sulfobromophthalein transport in the presence and absence of divalent cations was not due to ecto-ATPase activity but rather to alteration in [ATP4-]. Although an ATP4- receptor in macrophages mediates increased cellular permeability, reduced organic anion permeability is seen in hepatocytes. This effect is not seen in the hepatoma cell line HepG2. Modulation of activity of the organic anion transporter by extracellular ATP may have important pathophysiological consequences in conditions resulting in liver cell injury.
...
PMID:Extracellular ATP4- modulates organic anion transport by rat hepatocytes. 834 Mar 70

In the epithelial cell line FRT, derived from rat thyroid, extracellular ATP, at a concentration as low as 1 x 10(-7) M, specifically increases cytosolic Ca++ two fold over the basal level of 255 +/- 45 nM. A maximum increase of 5 fold over basal is seen at 1 x 10(-5) M ATP. The effect occurs in the absence of any measurable phosphatidyl inositol metabolism and requires the presence of extracellular Ca++, but is independent of extracellular Na+; it is duplicated by ATP gamma S but not by adenosine, AMP, ADP, AMP-PNP, AMP-CPP, or AMP-PCP. In the presence of the P2-receptor antagonist suramin, the ATP induced Ca++ influx is completely inhibited, whereas Mg++, La , and verapamil are ineffective. It appears that the most likely (and unique) mechanism of ATP induced increase of cytosolic Ca++ in FRT cells in an increased influx through the activation of a P2 receptor operated Ca++ channel.
...
PMID:Purinergic (P2) receptor-operated calcium entry into rat thyroid cells. 836 91

3'-O-(4-benzoyl)benzoyl ATP (BzATP) was used as a photoaffinity analog of ATP to label potential ATP receptors in ciliated cells. Like ATP, without photoactivation, BzATP stimulated the ciliary beat frequency in tissue culture up to threefold. Irradiation of intact cells in the presence of [alpha-32P]BzATP followed by SDS-PAGE and autoradiography revealed two labeled proteins with molecular masses of 46 and 96 kDa (p46 and p96). Photolabeling of both proteins was susceptible to digestion with trypsin, implying that the labeled proteins are at least partially exposed on the extracellular surface of the plasma membrane. The dependence of 32P incorporation in both proteins on [alpha-32P]BzATP concentration was similar. Labeling of p46 but not p96 required Ca2+ or Mg2+. Various nucleotides stimulated the ciliary frequency, and inhibited the photolabeling of p46 and p96. The rank order of apparent affinity for p46 is: ATP approximately equal to ADP > GTP gamma S > ADP beta S, UTP, 2MeSATP, AMP-PNP > AMP-PCP > AMP > adenosine; for p96 it is: ADP approximately equal to ADP beta S > or = ATP >> AMP-PCP, AMP-PNP > GTP gamma S > or = AMP > 2MeSATP, UTP, adenosine. The rank of stimulation of ciliary beat frequency is: ADP beta S, UTP > or = 2MeSATP, GTP gamma S, AMP-PNP, ATP > or = ADP > AMP-PCP > adenosine > AMP. These results suggest the involvement of p46 in the stimulatory effect of extracellular ATP on the ciliary beat, as a P2 purinoceptor. On the other hand, p96 may represent a P2 purinoceptor or an ectonucleotidase.
...
PMID:Extracellular ATP binding proteins as potential receptors in mucociliary epithelium: characterization using [32P]3'-O-(4-benzoyl)benzoyl ATP, a photoaffinity label. 853 Dec 2


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---