Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of peroxidation on 5'-nucleotidase activity as well as on membrane microviscosity has been investigated in liver plasma membranes from Wistar rats. The peroxidation was performed with 100 microM H2O2 and 200 microM FeSO4 and/or with 5 mM t-butylhydroperoxide. Treatment of the membranes with these oxidizing agents resulted in an elevation of the transition temperatures of the polarization of the lipid fluorescent probes 1,6 diphenyl-1,3,5 hexatriene (DPH), 3-p-(6-phenyl) 1,3,5 hexatriene phenylpropionic acid (PA-DPH) as well as of the fluorescent thiol reagent N-(1-pyrene) maleimide (1-PM). The peroxidation resulted in a decrease of the activity of 5'nucleotidase. Our data support that the increase of membrane microviscosity of the lipid domain regulates the activity of 5'-nucleotidase.
Cell Mol Biol 1992 Jul
PMID:Lipid peroxidation causes an increase of lipid order and a decrease of 5'-nucleotidase activity in the liver plasma membrane. 149 43

The contribution of 5'-nucleotidase and AMP-deaminase to adenine nucleotide degradation in human cardiomyocytes isolated from diseased or normal heart was investigated. The preparation used contained 30 to 50% of viable cells and the nucleotide degradation was stimulated by addition of deoxyglucose and oligomycin. To distinguish pathways of nucleotide degradation, adenosine deaminase was inhibited by erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA). Under these conditions, ATP concentration was decreased by 60% after 45 min of incubation. Simultaneously, increases in intra- and extracellular catabolite concentrations have been observed. Adenosine was the predominant catabolite found in both the cells and in the extracellular medium accounting for more than 70% of all degradation products. Intracellular adenosine concentration rose to 300 times greater than that outside the cell. An increase in intra- and extracellular inosine was also seen. Only a small increase of IMP concentration was observed. No hypoxanthine accumulation was found. No significant change in initial adenine nucleotide concentrations were observed in isolated cells during aerobic incubation without deoxyglucose and oligomycin. In conclusion, a pathway involving adenosine production appears to be the principal route of nucleotide degradation in human cardiomyocytes.
J Mol Cell Cardiol 1992 Jan
PMID:Adenine nucleotide catabolism and adenosine formation in isolated human cardiomyocytes. 156 34

The metabolic fate of labeled hypoxanthine and inosine, degradation products of adenine nucleotides, was studied in cultured beating cardiomyocytes, in order to assess the physiological significance of their contribution to salvage nucleotide synthesis in the heart. Inosine and hypoxanthine were found to be incorporated into nucleotides by a similar rate, but in the presence of 8-aminoguanosine, a potent inhibitor of purine nucleoside phosphorylase (EC 2.4.2.1), the rate of inosine incorporation into nucleotides was markedly reduced (by 75%), indicating that inosine incorporation to IMP (inosinic acid) occurs following its degradation to hypoxanthine. The proportion of hypoxanthine converted to IMP by hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) is markedly greater than that degraded to xanthine and uric acid by xanthine oxidase (EC 1.3.2.3). However, close to 50% of the IMP formed was degraded to inosine by IMP 5'-nucleotidase (EC 3.1.3.5). The results demonstrate the activity of the following futile cycle in the cardiomyocytes: hypoxanthine----IMP----inosine----hypoxanthine. The rational for the activity of this energy consuming cycle is yet unclear.
J Mol Cell Cardiol 1992 Feb
PMID:Metabolic fate of hypoxanthine and inosine in cultured cardiomyocytes. 158 1

Subcellular fractionation studies in resting human neutrophils indicated a bimodal distribution for cytochrome b. A major peak of cytochrome b co-sedimented with gelatinase under different experimental conditions. This localization was partially overlapped with specific granules (using lysozyme and lactoferrin as specific granule markers), but clearly resolved from azurophilic granules, plasma membrane, mitochondria, as well as from a novel alkaline phosphatase-rich intracellular organelle. A minor localization of cytochrome b was found in fractions enriched in both the plasma membrane marker 5'-nucleotidase and alkaline phosphatase. A significant portion of ubiquinone cell content co-fractionated with the gelatinase-containing granules. After phorbol myristate acetate (PMA)-cell stimulation, cytochrome b was mobilized to fractions showing respiratory burst activity and enriched in 5'-nucleotidase activity. This mobilization paralleled secretion of gelatinase and lysozyme to the extracellular medium. Furthermore, neutrophil stimulation with fluoride in the absence of cytochalasin B induced release of gelatinase and generation of superoxide anion with only minimal release of lysozyme. Preincubation of cells with the anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) prevented lysozyme release, but had only a minor effect on the release of gelatinase and did not inhibit the superoxide anion generation elicited by N-formyl-methionyl-leucyl-phenylalanine or PMA. These results suggest a main location of cytochrome b in mobilizable gelatinase-containing granules, which can constitute a subpopulation of specific granules. Furthermore, these findings show that the gelatinase-containing granule is functionally involved in the respiratory burst in neutrophils and that membrane fusion between plasma membrane and the gelatinase-containing granule occurs during activation of cells.
Mol Cell Biochem 1991 Jun 26
PMID:Cytochrome b co-fractionates with gelatinase-containing granules in human neutrophils. 165 2

An increase in the amount of actin associated with the plasma membrane was visualized by immunocytochemistry 5 min after the addition of insulin to Krebs II ascites tumour cells maintained in serum-free medium. At 1 h of incubation the rim of fluorescence at the plasma membrane as measured by image analysis, was about 30% more intense than in control cells indicating that the initial accumulation of actin at the plasma membrane was not of a transient nature. Since an increase in the total cellular actin content in ascites cells did not occur until after a lag period of about 15 min then the increased amount of actin at the plasma membrane seen at 5 min was attributed to a stimulation of the polymerization of actin. An increase in the association of actin at the plasma membrane was also observed in 3T3 fibroblasts in areas of membrane ruffling, while in some cells there was also increased actin accumulation in the perinuclear area. The putative plasma membrane-microfilament linking protein 5'-nucleotidase was shown to be present in association with actin in the cytoskeletal fraction. Incubation of cells with insulin resulted in a shift of the enzyme toward the bottom of gradients indicating association with actin filaments of a greater length. The results demonstrate that insulin causes a stimulation of actin polymerization and that the hormone can be therefore assigned a role in the regulation of the cytoskeleton.
Mol Cell Biochem 1991 Nov 13
PMID:Insulin induces changes in the subcellular distribution of actin and 5'-nucleotidase. 177 Sep 46

The controversial subject of the subcellular location of myocardial adenosine production was studied employing density gradient fractionation of heart muscle combined with a novel method for analyzing distribution profiles based on multiple regression (correlation) analysis. Bungarotoxin binding, N-acetyl-beta-D-glucosaminidase, cytochrome c oxidase, NADPH-dependent cytochrome c reductase and lactate dehydrogenase were used as markers for the plasma membrane, lysosomes, mitochondria, sarcoplasmic reticulum and cytosol, respectively. The normalized distribution frequencies (fraction of total) of 5'-nucleotidase in mitochondria, lysosomes, plasma membranes, sarcoplasmic reticulum and cytosol in the 50 x g supernatant of total homogenate of heart muscle were found to be 0, 0.25, 0.44, 0.08 and 0.23, respectively. To increase the resolution power of this approach with respect to mitochondria, a crude mitochondrial fraction was also studied, in which the normalized distribution of 5'-nucleotidase in the homogenate was 0, 0.16 and 0.84 in mitochondria, plasma membranes and lysosomes, respectively. This mainly lysosomal 5'-nucleotidase activity was 61% inhibited by the alpha,beta-methylene analog of ADP, indicating that although the latter has been considered specific to the plasma membrane enzyme, it also inhibits the lysosomal enzyme. The intercellular distribution of 5'-nucleotidase was not studied, but the lack of this enzyme in the mitochondria indicate that the adenosine production observed during mitochondrial AMP production, e.g. during acetate oxidation in intact heart muscle, must involve AMP transport out from the mitochondria.
J Mol Cell Cardiol 1990 Jul
PMID:Subcellular distribution of myocardial 5'-nucleotidase. 223 47

Carbovir (CBV) is a highly selective carbocyclic nucleoside inhibitor of HIV replication in human lymphocytes and is potentially useful in the treatment of AIDS [Vince et al. (1988) Biochem. Biophys. Res. Commun. 156, 1046-1053]. Using human lymphoid cells severely deficient in nucleoside kinases, we were able to identify the route of activation of CBV metabolism. The present studies have demonstrated that CBV is anabolized to the mono-, di-, and triphosphates and to guanosine 5'-triphosphate in CCRF-CEM cells. Conversion to GTP amounted to 15-20% of the total analogue nucleotides formed in the cells and may arise from CBV through depurination and salvage via HGPRT. Evidence was obtained that neither deoxycytidine kinase, adenosine kinase, or mitochondrial deoxyguanosine kinase is primarily involved in the initial step of phosphorylation of CBV in CCRF-CEM cells. In contrast, earlier studies [Johnson & Fridland (1989) Mol. Pharmacol. 36, 291-295] showed that a cytosolic 5'-nucleotidase catalyzes the activation of CBV to the monosphosphate. Other biochemical effects examined showed that the nucleobases hypoxanthine and adenine, but not guanine, their respective nucleosides, and the dideoxynucleosides 2',3'-dideoxyinosine, 2',3'-dideoxyguanosine, and 3'-azido-3'-deoxythymidine produced significant increased accumulation of CBV nucleotides in CEM cells. The exact mechanism for this potentiation of CBV phosphorylation has not been elucidated but may be due to a modulating effect of intracellular nucleotides on 5'-nucleotidase activity.
 ...
PMID:Metabolism of the carbocyclic nucleoside analogue carbovir, an inhibitor of human immunodeficiency virus, in human lymphoid cells. 227 22

KT5926, (8R*,9S*,11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-14-n-propoxy-2,3 ,9, 10-tetrahydro-8,11-epoxy, 1H,8H, 11H-2,7b,11a-triazadibenzo[a,g]cycloocta[cde] trinden-1-one, was found to be a potent and selective inhibitor of myosin light chain kinase. The compound inhibited both Ca2+/calmodulin-dependent and -independent smooth muscle myosin light chain kinases to a similar extent. The inhibition was not affected by the concentration of calmodulin. Kinetic analyses showed that the mode of inhibition was of the competitive type with respect to ATP (Ki, 18 nM) and of the noncompetitive type with respect to myosin light chain (Ki, 12 nM). These results indicated that KT5926 directly interacted with the enzyme at the catalytic site. KT5926 also inhibited other protein kinases, but with relatively high Ki values; the values for protein kinase C, cAMP-dependent protein kinase, and cGMP-dependent protein kinase were 723, 1200, and 158 nM, respectively. Ca2(+)-ATPase, Na+/K(+)-ATPase, hexokinase, and 5'-nucleotidase were not inhibited by KT5926 at less than 10 microM. The effect of KT5926 on serotonin secretion and protein phosphorylation induced by platelet-activating factor or phorbol ester was examined in rabbit platelets. KT5926 inhibited the phosphorylation of a 20-kDa protein but had no effect on the phosphorylation of a 40-kDa protein, thereby indicating that the compound exerts its selective inhibition of myosin light chain kinase in intact cells. The compound inhibited serotonin secretion induced by platelet-activating factor, but its potency was significantly less than that of K-252a, (8R*,9S*,11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-2,3,9, 10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b, 11a-triazadibenzo[a,g]cycloocta [cde]trinden-1-one, which inhibited the phosphorylation of both the 20-kDa protein and the 40-kDa protein. Phorbol ester-induced secretion was not suppressed by KT5926. These results provide the evidence that both the 20-kDa protein phosphorylation by myosin light chain kinase and the 40-kDa protein phosphorylation by protein kinase C substantially contribute to the secretion response in platelets.
Mol Pharmacol 1990 Apr
PMID:KT5926, a potent and selective inhibitor of myosin light chain kinase. 232 35

The effect of insulin on human red blood cells was investigated, both on intact cells and on isolated plasma membranes, testing the responsiveness of membrane-bound enzymes--such as (Na+-K+)-ATPase and 5'-nucleotidase--as well as the ouabain binding and ionic fluxes. It appears that insulin stimulates Na-pumping mechanisms increasing (Na+-K+)-ATPase activity through an enhanced availability of pumping sites, as can be inferred from the increased ouabain binding. The apparent unresponsiveness of fluorescence polarization parameters, following insulin treatment of isolated plasma membranes and intact cells, rules out--at present--an involvement of membrane lipid fluidity in the mechanism of action of insulin on human erythrocytes.
Mol Cell Endocrinol 1986 Jul
PMID:Insulin effects on human red blood cells. 242

5'-Amino-2',5'-dideoxythymidine (5'-AdThd) is a nontoxic thymidine (dThd) analogue capable of antagonizing the feedback inhibition exerted by thymidine triphosphate (dTTP) on thymidine kinase (EC 2.7.1.21). In intact cells, this results in stimulation of thymidine uptake by 5'-AdThd. We have studied the interaction between 5'-AdThd and thymidine kinase purified from 647V cells. We found that 5'-AdThd inhibited competitively thymidine kinase activity (Ki of 0.5 microM) in the absence of dTTP whereas dTTP inhibited thymidine kinase activity in a noncompetitive manner. However, in the presence of dTTP, 5'-AdThd was able to stimulate enzyme activity in a mode that suggests competition with dTTP for the regulatory site. Altered interactions were observed at high substrate (dThd) concentrations, with dThd showing competitive kinetics with dTTP. In intact cells, we evaluated the hypothesis that antagonism of feedback inhibition could account for stimulation of dThd uptake by 5'-AdThd. If inhibition of thymidine kinase activity by dTTP is critical, then depletion of cellular dTTP by methotrexate should reduce the ability of 5'-AdThd to stimulate dThd uptake. Indeed, this was the case. If the dTTP pools were repleted by the addition of higher concentrations of dThd, the ability of 5'-AdThd to stimulate dThd uptake was restored. Furthermore, effects of 5'-AdThd on nucleoside phosphorylase or cytoplasmic 5'-nucleotidase activity (dTMP breakdown) could not account for the stimulation of dThd uptake in 647V cells. In summary, our results indicate that 5'-AdThd interacts with thymidine kinase at the dTTP-binding site, resulting in stimulation of enzyme activity and stimulation of dThd uptake in intact cells.
Mol Pharmacol 1989 Jan
PMID:Enzyme regulatory site-directed drugs: study of the interactions of 5'-amino-2', 5'-dideoxythymidine (5'-AdThd) and thymidine triphosphate with thymidine kinase and the relationship to the stimulation of thymidine uptake by 5'-AdThd in 647V cells. 253 72


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