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:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of phosphatidylinositol-specific phospholipase C (PIase C) in a) the enigmatic phosphatidylinositol (PI) turnover and b) in our understanding of membrane enzyme-PI interactions is the subject matter of this article. PIase C is present in both procaryotes and eukaryotes. This enzyme is considered to be involved in the cells PI breakdown which occurs in response to several external stimuli. Recent information on the physical properties, Ca2+ requirement, cellular localization and modulation of the activity of PIase C of mammalian systems can help to evaluate the PI turnover from a new angle. Existing evidence suggests that Ca2+-dependent PI breakdown is probably mediated through the cytosolic and particulate PIase C while a Ca2+ independent pathway is catalyzed by a lysosomal enzyme. Apparently PI turnover may be operating through more than one mechanism. The association of this phenomenon with a membrane receptor event linked with "Ca2+ gating" may have to be reconsidered. Modulation of the PIase C activity by unsaturated amphiphiles or the presence of this enzyme in different physico-chemical forms could be a potential regulatory feature. Hydrolysis of membrane PI of a number of cells and tissues by the bacterial PIase C has been shown to cause substantial release of acetylcholinesterase, alkaline phosphatase and 5'-nucleotidase in free, soluble form. Other membrane enzymes, e.g., alkaline phosphodiesterase I, L-leucyl-beta naphthyl amidase and Ca2+ or Mg2+ ATPase are not affected. These results indicate a specific interaction between PI and certain enzymes in membranes. The chemical nature of this linkage, whether it is covalent or non-covalent, has also been explored and has provided intriguing insight into this phenomenon. New findings also indicate that hydrolysis of PI by PIase C also can cause modifications in membrane-enzyme activities, e.g., adenylate cyclase.
...
PMID:Minireview. Phosphatidylinositol specific phospholipases C. 708 67

The relationship between adenylate cyclase activity in the synaptic membrane fraction (M1) of rat brain and lipid peroxidation of these membranes was examined. In the presence of 5 mM dithiothreitol (DTT), 1 to 10 microM Fe/+ activated adenylate cyclase 2- to 4-fold. Of several metal ions, Fe2+ was the most effective. Other enzymes in M1, such as Mg2+-ATPase, (Na+-K+)-ATPase, 5'-nucleotidase, acetylcholinesterase, and phosphodiesterase, were not activated by Fe2+ plus DTT. Activation of adenylate cyclase by Fe2+ plus DTT was accompanied by production of malondialdehyde, a product of lipid peroxidation. Formation of malondialdehyde was completely parallel with enzyme activation. Ascorbic acid or a NADPH system also stimulated enzyme activity and caused lipid peroxidation. Activation of the enzyme and lipid peroxidation induced by Fe2+ plus DTT, ascorbic acid, or NADPH was completely prevented by simultaneous addition of N,N'-diphenyl-p-phenylenediamine, an inhibitor of lipid peroxidation. This inhibitor also prevented the decrease in turbidity of the enzyme preparation induced by Fe2+ plus DTT. The stimulatory effects of NaF, guanylyl-5'-imidodiphosphate and calmodulin, respectively, and that of Fe2+ plus DTT on the enzyme activity were additive. Activation of adenylate cyclase by Fe2+ plus DTT was only observed in brain synaptic membranes, not in erythrocyte ghosts, liver plasma membranes, or cardiac sarcolemma. These results indicate that lipid peroxidation of synaptic membranes was accompanied by specific stimulation of adenylate cyclase activity.
...
PMID:Activation of adenylate cyclase of rat brain by lipid peroxidation. 721 51

Axolemma-enriched fractions were isolated from the white matter of bovine corpus callosum via a purified preparation of myelinated axons which were osmotically shocked and fractionated on a discontinuous density gradient. Two membrane fractions of differing density were obtained: both were somewhat enriched over white matter whole homogenate in specific activity of acetylcholinesterase and 5'-nucleotidase and maximal binding capacity for saxitoxin. Both membrane fractions contained appreciable amounts of 2', 3'-cyclic nucleotide 3'-phosphohydrolase; the specific activity of antimycin-sensitive NAPH-cytochrome c reductase and cytochrome c oxidase indicated low levels of contamination by microsomal and mitochondrial membrane. The myelin which is concomitantly isolated with the axolemma-enriched fractions has a lipid and protein composition comparable to that of myelin isolated by other procedures. Both axolemma-enriched fractions contain about one half of their dry weight as lipid comprised of approximately 25% cholesterol, 25% galactolipid (cerebrosides and sulfatides in a molar ratio of about 4:1) and 50% phospholipid, mostly choline phosphatides and ethanolamine phospholes in an equimolar ratio. The axolemma fractions are also enriched in ganglioside content relative to the myelin fraction. The polypeptides of the axolemma-enriched fractions range from 20,000 to over 200,000 in molecular weight; the predominant proteins are in the range from 50,000 to 69,000. The most dense axolemma-enriched fraction is over fourfold enriched in glycoprotein content compared with myelin, with at least 10 different molecular-weight classes of glycoproteins as identified by Schiff stain of polyacrylamide gel protein profiles. The differences and similarities in the molecular composition of axolemma-enriched preparations which have been characterized to date are discussed.
...
PMID:Composition of axolemma-enriched fractions isolated from bovine CNS myelinated axons. 727 11

A membrane vesicle preparation was used to examine characteristics of the human placental cholinergic system. Plasma membrane vesicles were prepared from the microvillous surface of the human placental syncytiotrophoblast. Membranes were purified 18 -to 20-fold as indicated by 5'-nucleotidase activity. Vesicle cholinesterase activity was enriched and had a substrate preference consistent with that of acetylcholinesterase (acetylcholine greater than acetyl-beta-methylcholine greater than butyryl-choline). Choline acetyltransferase specific activity was reduced 80%. The synthetic muscarinic ligand, [3H]-quinuclidinyl benzilate (QNB), was used to identify two classes of muscarinic cholinergic binding sites. The dissociation constant of QNB binding was 80 pM and 30 nM for the two sites. The sites were saturable and bound 9 fmoles and 910 fmoles per mg protein for the high and low affinity sites, respectively. Specific binding was inhibited by scopolamine, atropine, carbamylcholine (CCH), and diphenhydramine, but not by non-muscarinic ligands-i.e. GABA, glycine, d-amphetamine, kappa-bungarotoxin and nicotine. The cholinergic agonist CCh had no effect on active AIB transport, although pharmacologic doses (lmM) of atropine, scopolamine and lidocaine reduced Na-gradient active transport of kappa-aminoisobutyric acid (AIB). No effect on Na-independent AIB transport was observed. Thus, these drugs apparently reduced AIB uptake through their shared local anesthetic activity and not through a central cholinergic mechanism. In contrast, CCh was able to stimulate Ca2+ uptake by the vesicles in a dose-dependent manner paralleling its ability to inhibit QNB binding. The CCh-stimulated Ca2+ uptake was inhibited by scopolamine, implying its mediation via cholinergic-type binding sites. The membrane vesicle preparation therefore provides a useful model for examination of the role of the human placental cholinergic system.
...
PMID:Syncytiotrophoblast membrane vesicles: a model for examining the human placental cholinergic system. 733 61

Semi-purified diets supplemented with either a high alpha-linolenate (n - 3) (perilla) oil or a high linoleate (n - 6) (safflower) oil were fed to rats through two generations. Rats fed safflower oil showed a decrease in docosahexaenoic acid (n - 3) and a compensatory increase in docosapentaenoic acid (n - 6) in all the brain regions and organelles examined, when compared with rats fed perilla oil. As reported previously, the safflower oil-fed rats exhibited inferior learning ability compared with the perilla oil-fed rats (N. Yamamoto et al., J. Lipid Res. 28, 144 (1987)). Using brains of rats in these dietary groups, the activities of several enzymes, Na+ , K+-ATPase, Ca2+-ATPase, 5'-nucleotidase, 2',3'-cyclic nucleotide phosphodiesterase, acetylcholinesterase, and choline acetyltransferase in membranes, were compared. The 5'-nucleotidase activity in cortex and hippocampus, and the Na+, K+-ATPase activity in myelin decreased slightly but significantly in the safflower oil group. None of the other membrane-associated enzyme activities in all the brain regions and organelles examined was affected significantly by the dietary fatty acids under optimal assay conditions in vitro. However, in the safflower oil group, the Na+, K+-ATPase activity of synaptosomes at a suboptimal concentration of ATP was 78% that in the perilla oil group. These results suggest that relatively large changes in the proportions of n - 3 and n - 6 polyunsaturated fatty acids in brain membranes caused by dietary manipulation do not provoke significant alterations in most membrane-bound enzyme activities. However, a small but significant change in Na+, K+-ATPase activity at a suboptimal concentration of ATP may be implicated in the altered learning behavior reported earlier.
...
PMID:Effect of a high alpha-linolenate and high linoleate diet on membrane-associated enzyme activities in rat brain--modulation of Na+, K+- ATPase activity at suboptimal concentrations of ATP. 749 79

The activity of acetylcholinesterase (AChE), 5'-nucleotidase (NT) and adenylate cyclase (AC) were studied in sensomotor cortex and neostriatum (NS) from right and left hemispheres of control and experimental rats, trained to perform food reaching with pushing on operant by preferable forepaw. The levels of summarized bilateral activity of NT as well as of AC were found to be similar in both studied structures of control rats, while the activity of AChE was higher in NS than in cortex. In trained rats the activity of AC was decreased both in cortex and NS, the activity of NT was decreased in cortex and increased in NS, AChE being not changed when compared with control. The bilateral values of enzyme activities in well and badly learning rats were significantly different. Meanwhile, when the dominant and subdominant hemispheres were compared these values were found to be similar. In general, the results obtained could be evaluated as specific features of conditioned unilateral manipulatory reactions, characteristic for cortex and NS of brain hemispheres.
...
PMID:[The neurochemical characteristics of the rat neostriatum and motor cortex after the acquisition of a unilateral manipulatory reflex]. 752 51

Indicators of the activity of acetylcholinesterase (ACE), 5'-nucleotidase (NT), adenylate cyclase (AC) in the sensorimotor cortex and the neostriatum (NS) of the right and left cerebral hemispheres of control rats and rats trained to perform a food-procuring movement by pressing against an obstacle with the forelimb. An identical level of the averaged bilateral values of the activity of NT and AC in both of the structures in question and an increased ACE activity in the NS were found in the control animals. After the development of a manipulatory skill, the activity of AC decreased in the cortex and the NS in the presence of unchanged ACE activity, while NT activity decreased in the cortex and increased in the NS. The bilateral values of the activity of the enzymes differed significantly in well and poorly trained rats. At the same time, the activity of the enzymes was similar in character in the dominant and subdominant hemispheres for each group of animals. Overall the neurochemical changes obtained can be regarded as specific correlates of the developed unilateral manipulatory reactions that are characteristic for the structures in question of both cerebral hemispheres.
...
PMID:Neurochemical characteristics of the rat neostriatum and motor cortex after the development of a unilateral manipulatory reflex. 763 Apr 91

A competitive antagonist of the N-methyl-D-aspartate receptor, CGP 39551, was administered daily to neonatal rats with increasing doses from postnatal day 1 to 22. These animals displayed approximately 50% decrease of body weight at the end of treatment and, therefore, both normal and neonatally undernourished rats were used as controls. At a young adult stage (55-75 days of age) CGP 39551-treated rats showed a much higher spontaneous locomotor activity as compared to control groups. This hypermotility was counteracted by D1 and D2 dopamine antagonists while administration of methamphetamine increased, to the same extent, the differential basal locomotor activity of treated and control groups. The locomotor activity response to the N-methyl-D-aspartate channel blocker, dizocilpine maleate, was significantly shifted to the right for treated rats so that an equivalent increase of motility was obtained by doubling the dose effective for control animals. In in vivo microdialysis experiments, similar amounts of dopamine were collected from the striatum of treated and control rats after high K+ or methamphetamine stimulation, the only difference being a greater Ca2+ dependency of the depolarization-induced dopamine release in treated rats. Assays for different neurochemical parameters, carried out at 80-90 days of age, suggested some alteration of the balance between excitatory and inhibitory circuits in the basal ganglia of CGP 39551-treated rats. Tyrosine hydroxylase and calbindin immunostaining, as well as acetylcholinesterase histochemistry, revealed a similar picture in the striatum of treated and control rats. However, 5'-nucleotidase histochemistry showed a stronger and evenly distributed reactivity in the striatum of treated rats, opposite to the weaker and patchy localization of normal or undernourished controls. From the present results it is possible to conclude that chronic blockade of the N-methyl-D-aspartate receptor during neonatal brain maturation results in long-lasting alteration of locomotor activity which appears related to functional changes of the dopamine receptors as well as to an altered balance between various excitatory and inhibitory neurotransmitter and neuromodulatory systems.
...
PMID:Long-lasting effects of chronic neonatal blockade of N-methyl-D-aspartate receptor through the competitive antagonist CGP 39551 in rats. 791 9

The subcellular distribution of the adenosine A2a receptor in rat striatum has been investigated using specific binding of the A2a-selective ligand [3H]-CGS 21680. After subcellular fractionation, the distribution of [3H]-CGS 21680 binding was similar to that of the cholinergic nerve terminal marker acetylcholinesterase rather than the more general membrane marker 5'-nucleotidase, with 42% of binding associated with the synaptosomal sub-fraction and 19% with a light membrane fraction. Binding of [3H]-CGS 21680 was also found to co-purify with the cholinergic nerve terminal marker choline acetyltransferase during immunoaffinity purification of striatal cholinergic nerve terminals. These results demonstrate that some adenosine A2a receptors are present on cholinergic nerve terminals in rat striatum.
...
PMID:The subcellular distribution of [3H]-CGS 21680 binding sites in the rat striatum: copurification with cholinergic nerve terminals. 836 37

The activity of acetylcholinesterase (AChE), adenylate cyclase (AC), 5'-nucleotidase (NT), Na+, K(+)-ATPase, as well as the contents of phospholipids (PL) and gangliosides (G) per mg of protein in homogenate, crude membrane (P2) fraction, and synaptosomes from the sensorimotor cortex of the right and left hemispheres of rat brain were analyzed under normal and hypoxic conditions. The authors found that under normal physiological conditions there are no significant differences of the studied parameters in homogenates of sensorimotor cortex from the right and left hemispheres. In P2 fractions, and especially in preparations of synaptosomes from the right and left cortex, differences in the activity of 5'-NT and AC were found. Hypoxia (pO2 = 7.8%) was shown to alter studied parameters (AChE, AC, Na+, K(+)-ATPase activity, and PL content) mainly in the right hemisphere.
...
PMID:Hypoxic hypoxia induces different biochemical changes in the cortex of the right and left hemispheres of rat brain. 853 26


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

---