Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasma membranes, microsomes, and mitochondria were isolated from mouse fibroblast (LM) suspension cells by modification of several established procedures. Choline analogues such as N,N'-dimethylethanolamine, N-monomethylethanolamine, or ethanolamine were incorporated in vivo into phospholipids of all three cell fractions studied, but to varying degrees depending on the type of analogue used. The in vivo incorporation of these bases into membrane phospholipids produced no significant effect on the activities of seven membrane-bound enzymes: (Na+, K+)-ATPase, 5'-nucleotidase (plasma membranes); TPNH-cytochrome c reductase, glucose-6-phosphatase, inosine diphosphatase (microsomes); and succinate cytochrome c reductase (mitochondria). The incorporation of base analogues into phospholipids was accompanied by several compensatory mechanisms. (a) The quantity of both phosphatidylcholine and phosphatidylethanolamine decreased up to 75% and 50% respectively in 3 days. (b) The molar ratio of desmosterol/phospholipid in the plasma membranes of LM cells grown in suspension culture in the presence of choline analogues decreased from 0.65 to 0.45. (c) The percentage of lysophosphatidylcholine increased over 2-fold in the phospholipid of all subcellular fractions studied. The quantity of lysophosphatidylcholine was directly proportional to the number of methyl groups on the nitrogen atom of the base analogue supplemented to the cells. This was a specific effect since the quantity of lysophosphatidylethanolamine, the other major lysophospholipid, remained unchanged. (d) The ratio of zwitterionic phospholipids to acidic phospholipids remained relatively constant in all isolated membrane fractions regardless of analogue supplementation. Neither increase in the degree of unsaturation nor shortening of fatty acid chain length was noted in response to analogue supplementation.
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PMID:Isolation and characterization of subcellular membranes with altered phospholipid composition from cultured fibroblasts. 95 75

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.
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PMID:Subcellular distribution of myocardial 5'-nucleotidase. 223 47

Isopycnic centrifugation experiments using sucrose density gradients showed that in digitonin-treated microsomes the distribution of the plasma membrane (PM) marker 5'-nucleotidase was shifted to higher densities. The treatment also caused similar but less pronounced changes in the distribution of protein, the putative endoplasmic reticulum (ER) marker NADPH-dependent cytochrome c reductase, and the inner mitochondrial marker cytochrome c oxidase. Similar experiments using more purified membrane fractions showed that the digitonin treatment led to a comparable increase in the densities of the fractions N1 and N2 previously described as subfractions of plasma membrane and to considerably less increase in the density of the fraction N3B which is enriched in the endoplasmic reticulum and the inner mitochondrial markers. Digitonin inhibited the ATP-dependent Ca uptake by the N1 fraction in a concentration-dependent manner (I50 = 0.3 mg/mL). Digitonin (0.5 mg/mL) inhibited the ATP-dependent azide-insensitive Ca uptake by all the fractions. The results support the hypothesis that (a) N1 and N2 are subfractions of plasma membrane, and (b) ATP-dependent azide-insensitive Ca uptake in rat myometrium is a property of plasma membranes.
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PMID:Effect of digitonin on rat myometrium subcellular membrane fractions. 627 91

Distribution of specific binding sites for [3H]nitrendipine was studied in subcellular fractions isolated from rat gastric fundus smooth muscle and from rat myometrium. There was an excellent correlation between the distribution of [3H]nitrendipine binding determined at the nitrendipine concentrations of 0.138 and 1.38 nM, and the distribution of the plasma membrane markers K+-activated ouabain-sensitive p-nitrophenylphosphatase, 5'-nucleotidase, phosphodiesterase I, and Mg-ATPase, but not between the mitochondrial markers cytochrome c, oxidase, succinate-dependent cytochrome c reductase, or rotenone-insensitive NADH-dependent cytochrome c reductase or the putative endoplasmic reticulum marker NADPH-dependent cytochrome c reductase. The binding occurred with high affinity and with a similar (0.097-0.146 nM) equilibrium dissociation constant to all the fractions, even though the density of binding sites varied and was highest in the plasma membrane marker-enriched fractions. The maximal binding in the plasma membrane-enriched fraction from the rat gastric fundus smooth muscle was 0.43 +/- 0.04 pmol/mg, and in that from rat myometrium was 0.72 +/- 0.09 pmol/mg. Thus in the two smooth muscles studied the plasma membrane is the locus of the high affinity nitrendipine binding.
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PMID:Subcellular distribution of [3H]nitrendipine binding in smooth muscle. 632 63

Microsomal vesicles prepared from rat brain contain a Na+-Ca2+ exchange transport system capable of accumulating Ca2+ in a time- and temperature-dependent manner. The Ca2+ accumulated by these vesicles was released by the Ca2+ ionophore A23187 but not by EGTA. The Km value for Ca2+ uptake was 23 microM with a maximal velocity of 21 nmol Ca2+/mg per min. Ca2+ uptake was significantly inhibited by La3+, Sr2+, Mn2+ and Ba2+ and to a lesser extent by Mg2+. 45Ca2+ accumulated by Na+-dependent uptake could be released by 40Ca2+, indicating the presence of a Ca2+-Ca2+ exchange activity in the microsomes. Ca2+-Ca2+ exchange was stimulated in Li+- and K+-containing media as compared to choline+ media. Microsomes also catalyzed ATP-dependent Ca2+ uptake (in the absence of Na+ gradient). The Ca2+ sequestered by this mechanism could be released by extravesicular Na+, indicating that both the ATP-dependent and the Na+-dependent Ca2+ uptake systems are present in the same membrane. The microsomal preparation used did not contain measurable amounts of succinate dehydrogenase activity or oligomycin-azide-dinitrophenol sensitive ATP-dependent Ca2+ uptake. Thus, the Ca2+ accumulation observed was not due to contaminating mitochondria. The preparation was enriched for 5'-nucleotidase and (Na+ + K+)-ATPase (plasma membrane markers) as well as antimycin A-resistant NADPH-dependent cytochrome c reductase activity (an endoplasmic reticulum marker).
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PMID:Sodium-dependent and calcium-dependent calcium transport by rat brain microsomes. 679 24

A new method for measurement of transbilayer distribution of sterol in plasma membranes is reported. The procedure utilized a fluorescent sterol, dehydroergosterol, and a chemical quenching agent, trinitrobenzenesulfonic acid. Dehydroergosterol was useful as a probe molecule for sterols for the following reasons, (a) Dehydroergosterol contained no bulky side chains as reporter groups. (b) Dehydroergosterol structurally resembled cholesterol and desmosterol, the primary sterol synthesized by LM fibroblasts. (c) Dehydroergosterol interacted with digitonin, filipin, and served as a substrate for cholesterol oxidase. (d) The phase transition of dipalmitoylglycerophosphocholine was completely abolished by dehydroergosterol. (e) The native sterol of LM fibroblasts, desmosterol, was completely replaced by dehydroergosterol without effect on LM cell growth, cell doubling time, plasma membrane (Na+, K+)-ATPase and 5'-nucleotidase activity, microsomal NADPH-dependent cytochrome c reductase activity, and mitochondrial succinate-dependent cytochrome c reductase activity. (f) Neither the phospholipid composition nor the sterol/phospholipid ratio of LM fibroblasts were altered by supplementation with dehydroergosterol. The trinitrophenyl group of trinitrophenylglycine or of surface membranes of LM fibroblasts or red blood cells treated with trinitrobenzenesulfonic acid was an excellent quencher of dehydroergosterol fluorescence. Fluorescence in mouse very-low-density lipoproteins, LM fibroblasts plasma membranes, red blood cell surface membranes, and in rat red blood cell membranes was quenched 95 +/- 3%, 20 +/- 2%, 75 +/- 4%, and 69 +/- 4% respectively when the quenching agent was present on only the extracellular site of the membrane. Trinitrophenyl residues effectively quenched the dehydroergosterol fluorescence in the plasma membrane of LM cells by 20% when dehydroergosterol was present from 1-85 mol/100 ml of the membrane sterol. When both sides of the plasma membrane were trinitrophenylated, greater than 95% of the dehydroergosterol fluorescence was quenched. In addition, when LM cells were cultured with dehydroergosterol, exposed latex beads, and the endocytosed particles isolated as phagosomes and treated with trinitrobenzenesulfonic acid under non-penetrating conditions, the fluorescence of the dehydroergosterol was quenched nearly 64%. From these and other results we deduced that the inner monlayer of the LM fibroblasts plasma membrane was enriched with dehydroergosterol. In contrast, the distribution of the sterol in red blood cell membranes indicated an enrichment in the outer monolayer.
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PMID:Asymmetric transbilayer distribution of sterol across plasma membranes determined by fluorescence quenching of dehydroergosterol. 706 May 96