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)

Poliovirus replicase- and host factor-catalyzed copying of 3'-terminal polyadenylic acid [poly(A)] of poliovirion RNA was studied. Host factor-stimulated synthesis of polyuridylic acid [poly(U)] by the replicase required ATP in addition to UTP. ATP was not required for the oligouridylic acid-primed copying of 3'-terminal poly(A) of virion RNA. GTP, CTP, and AMP-PCP (5'-adenylyl beta-gamma methylenediphosphate, an ATP analog) could not replace ATP in host factor-stimulated synthesis of poly(U). Antibodies to poliovirus genome-linked protein (VPg) specifically precipitated in vitro-synthesized poly(U) from a host factor-stimulated reaction. The poly(U) synthesized in a host factor-stimulated reaction was shown to be attached to VPg precursor polypeptide(s) via a tyrosine-phosphate bond as found in poliovirion VPg-RNA.
...
PMID:ATP is required for initiation of poliovirus RNA synthesis in vitro: demonstration of tyrosine-phosphate linkage between in vitro-synthesized RNA and genome-linked protein. 632 50

A proline dipeptidase (EC 3.4.13.9) from guinea pig brain was purified to over 90% homogeneity by a combination of ammonium sulfate fractionation, DEAE-cellulose chromatography, calcium phosphate-cellulose chromatography, chromatofocusing, and gel filtration on Sephadex G-200. A purification factor of 2718-fold was obtained with a yield of 7%. The purified enzyme was found to have an apparent molecular weight of 132,000 and to consist of two dissimilar subunits of molecular weights 64,000 and 68,000. The substrate specificity of the enzyme is not that of a strict proline dipeptidase. Although it preferentially hydrolyzes proline dipeptides (Leu-Pro) it also hydrolyzes prolyl dipeptides (Pro-Leu) and dipeptides not containing proline (Leu-Leu). The purified enzyme preparation exhibited weak aminoacylproline aminopeptidase activity against Arg-Pro-Pro but it did not exhibit any post-proline dipeptidyl aminopeptidase, post-proline cleaving endopeptidase, proline iminopeptidase, prolyl carboxypeptidase or carboxypeptidase P activities when tested with a large variety of peptides and arylamides. With all of the proline and prolyl dipeptides examined the enzyme exhibited biphasic kinetics (two distinct slopes on Lineweaver-Burk plots). However, with Leu-Leu as substrate normal Michaelis-Menten kinetics were obeyed.
...
PMID:The purification and characterization of a proline dipeptidase from guinea pig brain. 685 81

1. Dialysed giant axons from the squid have been used to study some of the properties of the Na+ fluxes when the Na+ pump is fully inhibited by strophanthidin. 2. In axons which had been depleted of ATP, strophanthidin had no effect on Na+ efflux. Similar negative results were obtained in axons dialysed with and without internal or external K+, and with or without 100 microM-internal Ca2+. 3. In the presence of 60 mM-internal Na+, 440 mM-external Na+ and strophanthidin, the fluxes of Na+ had the following characteristics. (i) ATP stimulated an efflux and an influx of Na+ of similar magnitude. The K1/2 for ATP, measured from its effect on Na+ efflux, was about 200 microM. (ii) The non-hydrolysable ATP analogue adenylyl(beta, gamma-methylene)-diphosphonate (AMP-PCP), at 2 mM concentration, either alone or in combination with 2 mM-internal phosphate, failed to stimulate any efflux of Na+. (iii) The ATP-dependent Na+ efflux was not affected by removal of internal or external K+, or external Mg2+ or Ca2+, and was not dependent on internal Ca2+. (iv) within the resolution of the method, all the ATP-dependent Na+ influx required internal Na+, and all the ATP-dependent Na+ efflux required external Na+. From the magnitude of the unidirectional Na+ fluxes the stoichiometry seemed to be a 1 to 1 Na+--Na+ exchange. 4. The ATP-internal Na+-dependent influx of Na+ in the presence of strophanthidin was not affected by 1 mM-vandate in the dialysis solution, a concentration which fully inhibits the Na+ efflux through the Na+ pump that is activated by external K+. 5. In the presence of external Na+, the external K+ sites of the Na+ pump are completely saturated with 100 mM-external K+. In unpoisoned axons incubated with 100 mM-external K+, replacement of external Na+ with Tris+ produced no change in the efflux of Na+. However, in axons poisoned with 50 microM-strophanthidin, replacement of external Na+ with Tris+ resulted in a reversible inhibition of Na+ efflux. This could suggest that strophanthidin poisoning might induce Na+ (cations?) fluxes which are not present in normal conditions.
...
PMID:An ATP-dependent sodium-sodium exchange in strophanthidin poisoned dialysed squid giant axons. 731 Jul 19

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 present study addressed the hypothesis that the DA transporter ligand, [3H]mazindol, labels multiple sites/states associated with the dopamine (DA) transporter in striatal membranes. Incubations with [3H]mazindol proceeded for 18-24 hr at 4 degrees C in 55.2 mM sodium phosphate buffer, pH 7.4, with a protease inhibitor cocktail. In order to obtain data suitable for quantitative curve fitting, it was necessary to repurify the [3H]mazindol by HPLC before a series of experiments. Under these conditions, we observed greater than 80% specific binding. The method of binding surface analysis was used to characterize the interaction of GBR12935, BTCP, mazindol, and CFT with binding site/sites labeled by [3H]mazindol. A one site model fit the data as well as the two site model: Bmax = 16911 fmol/mg protein, Kd of [3H]mazindol = 75 nM, Ki of GBR12935 = 8.1 nM, Ki of CFT = 50 nM and Ki of BTCP = 44 nM. The inhibitory mechanism (competitive or noncompetitive) of several drugs (GBR12935, CFT, BTCP, cocaine, cis-flupentixol, nomifensine, WIN35,065-2, bupropion, PCP, and benztropine) was determined. All drugs inhibited [3H]mazindol binding by a competitive mechanism. Although the ligand-selectivity of the [3H]mazindol binding site indicates that it is the uptake inhibitor recognition site of the classic DA transporter, the quantitative differences among the ligand-selectivities of different radioligands for the same site suggest that each radioligand labels different overlapping domains of the DA uptake inhibitor recognition site. It is likely that development of domain-selective drugs may further our understanding of the DA transporter.
...
PMID:Studies of the biogenic amine transporters. 1. Dopamine reuptake blockers inhibit [3H]mazindol binding to the dopamine transporter by a competitive mechanism: preliminary evidence for different binding domains. 818 30

Rats learned to lever-press when such behavior was reinforced by microinjections of phencyclidine (PCP) directly into the ventromedial (shell) region of nucleus accumbens, indicating that the drug has direct rewarding actions in that region. Separate groups of rats learned to lever-press when reinforced with microinjections of dizoclipine (MK-801) or 3-((+/-)2-carboxypiperazin-4yl)propyl-1-phosphate (CPP), drugs known to block NMDA receptor function but not dopamine uptake, into the same region. Each drug was ineffective or markedly less effective when injected at a slightly more dorsal and lateral site in the core of nucleus accumbens. Self-administration of PCP, MK-801, or CPP directly into nucleus accumbens was not altered by co-infusion of a dose of the dopamine antagonist sulpiride that effectively blocked intracranial self-administration of the dopamine uptake inhibitor nomifensine, suggesting that the rewarding actions of the NMDA receptor antagonists are not dopamine-dependent. Rats also developed lever-pressing habits when PCP, MK-801, and CPP were each microinjected directly into frontal cortex, a region previously associated with the rewarding actions of cocaine but not nomifensine. Thus nucleus accumbens and frontal cortex are each potential substrates for the rewarding properties of PCP and related drugs, and the ability of these drugs to disrupt NMDA receptor function seems sufficient to account for their rewarding actions. When considered with independent evidence, the present results suggest a model of drug reward within which the critical event is inhibition of medium spiny neurons in nucleus accumbens.
...
PMID:Rewarding actions of phencyclidine and related drugs in nucleus accumbens shell and frontal cortex. 862 41

[3H]Ryanodine binding to, as well as functions of, ryanodine receptor intracellular Ca2+ release channel complexes are modulated by several adenosine-based compounds. In this study, we determined the effects of endogenous compounds termed diadenosine polyphosphates (ApnAs; n = 2-6 phosphate groups) on [3Hlryanodine binding to membranes prepared from rat brain and skeletal and cardiac muscle. Under low ionic strength buffer conditions, [3H]ryanodine binding to brain membranes was significantly increased by 171% with 333 microM P1,P5-di(adenosine-5') pentaphosphate (Ap5A) and by 209% with the same concentration of the metabolism-resistant ATP analogue betagamma-methyleneadenosine 5'-triphosphate (AMP-PCP) compared with control values for [3H]ryanodine binding of 9.6 +/- 1.8 fmol/mg of protein. Dose-related increases in [3H]ryanodine binding were observed for all five ApnAs tested [P1,P2-di(adenosine-5') pyrophosphate (Ap2A), P1,P3-di(adenosine-5') triphosphate (Ap3A), P1,P4-di(adenosine-5') tetraphosphate (Ap4A), Ap5A, and P1,P6-di(adenosine-5') hexaphosphate (Ap6A)] as well as AMP-PCP; oxidized salts of ApnAs stimulated [3H]ryanodine binding to a greater degree than did nonoxidized APnAs. The apparent rank order for the capacity of these agents to increase [3H]-ryanodine binding was oxidized Ap4A = oxidized Ap5A > oxidized Ap3A > Ap6A > AMP-PCP > Ap5A > AP2A. Addition of the approximate EC50 dose of oxidized Ap4A (37 microM) increased the affinity (KD) of ryanodine receptors from 34 +/- 7 to 12 +/- 2 nM, the apparent binding site density (Bmax) was not significantly different from control values of 107 +/- 33 fmol/mg of protein. Increases in [3H]-ryanodine binding by either oxidized Ap4A or nonoxidized Ap5A were not further enhanced by coincubation with AMP-PCP, which suggests a similar site of action for the ApnAs and AMP-PCP. [3H]Ryanodine binding to skeletal and cardiac muscle membranes was enhanced by addition of oxidized AP4A Ap5A, and AMP-PCP. Oxidized AP4A increased the specific binding by ninefold in skeletal muscle and by threefold in cardiac muscle. These results suggest that ApnAs, at physiologically relevant concentrations, may serve as endogenous modulators of ryanodine receptor-gated Ca2+ release channels.
...
PMID:Regulation of ryanodine receptor calcium release channels by diadenosine polyphosphates. 876 82

Cholecystokinin (CCK) receptors on rat pancreatic acinar cells display two binding affinity states in the presence of adeninine and guanine triphosphates with the effect of ATP mediated by the enzyme nucleoside diphosphate kinase. To determine whether this behavior was intrinsic to a single receptor protein we studied the binding affinity of CHO cells stably transfected with a cloned rat CCKA receptor. 125I-CCK binding to intact cells at 37 degrees C revealed two affinity states for CCK of Kd values 20 pM and 2.4 nM. Membranes prepared from these cells displayed a single affinity state for CCK but two affinity states could be restored in the presence of GTP[gamma S], ATP and ATP[gamma S] but not AMP-PCP. ATP and ATP[gamma S] but not AMP-PCP were substrates for nucleoside diphosphate kinase present in CHO cell membranes and transferred their terminal phosphate to GDP. These findings indicate that the interconvertible affinity states of the CCK receptor are inherent in a single receptor protein and that nucleoside diphosphate kinase mediates the effect of ATP to regulate these two affinity states.
...
PMID:Nucleotides regulate the binding affinity of the recombinant type A cholecystokinin receptor in CHO K1 cells. 885 9

Degradable hydroxyapatite (HA) implants complexed with the resorption inhibiting agent bisphosphonate (PCP) and the mineralizing agent alkaline phosphatase (ALP) can theoretically maintain alveolar bone mass directly after extraction of teeth. The present in vitro study investigated the surface properties of PCP-ALP-complexed HA implants in relation to the requirements of implant behavior and action. Adsorbed PCP (pH 3.49) resulted in a flattening and broadening of the phosphate peaks and the formation of carbonate peaks in the HA pattern of the implant indicating a chemical alteration of the HA surface. Adsorption of ALP onto PCP-altered HA surfaces was 26% lower than onto HA implant blank surfaces. PCP-ALP-complexed HA implants released the PCP and ALP steadily and continuously over observation periods of, respectively, 75 and 14 days. During these observation periods, the ceramic grains of the HA implant became smaller and intergrain boundaries became broader. These morphologic characteristics suggested preconditioning of the HA implant surface for future bonding and degradation in vivo. Individual grains were no longer bonded to other grains and detached from the implant which had become rounded in shape. From in vitro mice experiments we found that PCP concentrations between 10(-4) and 10(-3) M resulted in 45Ca-release from the bone HA. Our calculations showed, however, that only a total concentration of 1.4 x 10(-4) M PCP was gradually released over the whole observation period. In another experiment, it appeared that a PCP concentration in solution < 10(-3) M did not reduce ALP activity. It is concluded that release of PCP by the PCP-ALP-complexed implants is maintained at levels in the range to impair osteoclast bone resorption but not high enough to block osteoblast activity. The amount of ALP released can lead to induction of bone formation onto implant surfaces. pH-induced alterations in the microstructure and chemistry of the HA surface allow for controlled degradation of the HA implants in vitro. A PCP-ALP-complexed HA implant acting as temporary scaffolding for alveolar bone growth enhancement, mineralization, and maintenance seems to be a reasonable concept for preservation of the edentulous alveolus.
...
PMID:Degradable bisphosphonate-alkaline phosphatase-complexed hydroxyapatite implants in vitro. 928 69

We studied the ATP dependence of NHE-1, the ubiquitous isoform of the Na+/H+ antiporter, using the whole-cell configuration of the patch-clamp technique to apply nucleotides intracellularly while measuring cytosolic pH (pHi) by microfluorimetry. Na+/H+ exchange activity was measured as the Na(+)-driven pHi recovery from an acid load, which was imposed via the patch pipette. In Chinese hamster ovary (CHO) fibroblasts stably transfected with NHE-1, omission of ATP from the pipette solution inhibited Na+/H+ exchange. Conversely, ATP perfusion restored exchange activity in cells that had been metabolically depleted by 2-deoxy-D-glucose and oligomycin. In cells dialyzed in the presence of ATP, no "run-down" was observed even after extended periods, suggesting that the nucleotide is the only diffusible factor required for optimal NHE-1 activity. Half-maximal activation of the antiporter was obtained at approximately 5 mM Mg-ATP. Submillimolar concentrations failed to sustain Na+/H+ exchange even when an ATP regenerating system was included in the pipette solution. High ATP concentrations are also known to be required for the optimal function of other cation exchangers. In the case of the Na/Ca2+ exchanger, this requirement has been attributed to an aminophospholipid translocase, or "flippase.". The involvement of this enzyme in Na+/H+ exchange was examined using fluorescent phosphatidylserine, which is actively translocated by the flippase. ATP depletion decreased the transmembrane uptake of NBD-labeled phosphatidylserine (NBD-PS), indicating that the flippase was inhibited. Diamide, an agent reported to block the flippase, was as potent as ATP depletion in reducing NBD-PS uptake. However, diamide had no effect on Na+/H+ exchange, implying that the effect of ATP is not mediated by changes in lipid distribution across the plasma membrane. K-ATP and ATP gamma S were as efficient as Mg-ATP in sustaining NHE-1 activity, while AMP-PNP and AMP-PCP only partially substituted for ATP. In contrast, GTP gamma S was ineffective. We conclude that ATP is the only soluble factor necessary for optimal activity of the NHE-1 isoform of the antiporter. Mg2+ does not appear to be essential for the stimulatory effect of ATP. We propose that two mechanisms mediate the activation of the antiporter by ATP: one requires hydrolysis and is likely an energy-dependent event. The second process does not involve hydrolysis of the gamma-phosphate, excluding mediation by protein or lipid kinases. We suggest that this effect is due to binding of ATP to an as yet unidentified, nondiffusible effector that activates the antiporter.
...
PMID:ATP dependence of Na+/H+ exchange. Nucleotide specificity and assessment of the role of phospholipids. 904 42


<< Previous 1 2 3 4 5 6 Next >>

---