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

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enzyme activity that represents ouabain-insensitive, potassium-dependent p-nitrophenylphosphatase (p-NPPase) was assessed in rat atrial myocytes by biochemical and cytochemical procedures. No activity was detected in parallel experiments with ventricular myocytes. Fixed tissues were incubated in a reaction medium containing Tricine buffer, p-nitrophenylphosphate (p-NPP), KCl, MgCl2, CaCl2, CeCl3. Triton X-100, levamisole, and ouabain. Final pH was adjusted to 7.5. Biochemical studies showed that accumulation of p-nitrophenol in the medium was increased proportionally in accordance with the amount of incubated tissue. This activity was optimal with incubation at pH 7.5 and in the presence of KCl. Approximately 70% of the enzyme was inhibited by 2 mM CeCl3. Electron microscopic observations revealed reaction product (RP) at sites of ouabain-insensitive, potassium-dependent p-NPPase activity as electron-dense precipitate localized at the inner surface of the plasma membrane and at the T-tubules of atrial myocytes. Control experiments indicated that the activity was strongly inhibited by sodium orthovanadate and was repressed by omeprazole and 1,3-dicyclohexylcarbodiimide. X-ray microanalysis confirmed the presence of cerium within the cytochemical RP. The ouabain-insensitive, K-dependent p-NPPase activity detected in the present study is considered to be an isoform of a P-type, H-transporting, K-dependent adenosine triphosphatase (H,K-ATPase).
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PMID:Biochemical properties and cytochemical localization of ouabain-insensitive, potassium-dependent p-nitrophenylphosphatase activity in rat atrial myocytes. 901 8

We have already described the separation of two brain soluble fractions by Sephadex G-50, one of which stimulates (peak I) and the other inhibits (peak II) Na+, K(+)-ATPase and K(+)-p-nitrophenylphosphatase (K(+)-p-NPPase) activities. Here we examine the features of synaptosomal membrane p-NPPase activity in the presence and absence of brain peak I. It was observed that stimulation of Mg2+, K(+)-p-NPPase activity by peak I was concentration dependent. The ability of peak I to stimulate p-NPPase activity was lost by heat treatment followed by brief centrifugation. Pure serum albumin also stimulated enzyme activity. K(+)-p-NPPase stimulation by peak I proved dependent on K+ concentration but independent of Mg2+ and substrate p-nitrophenylphosphate concentrations. Since our determinations were performed in a non-phosphorylating condition reflecting the Na+, K(+)-ATPase Na+ site, it is suggested that peak I may stimulate the Na+-dependent enzyme phosphorylation known to take place from the internal cytoplasmic side.
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PMID:Kinetics of K(+)-p-nitrophenyl phosphatase stimulation by a brain soluble fraction. 901 48

Ion-transporting Na,K-ATPase plays an essential role in nerve conduction. To clarify the cytochemical effects of reserpine on transport Na,K-ATPase activity, the localization of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase (K-NPPase) activity was investigated in the facial nerves of normal and reserpinized guinea pigs using a cerium-based method. In the normal facial nerve, the reaction product of K-NPPase activity was observed on the internodal axolemma and Schmidt-Lanterman incisures. In the Ranvier nodes, enzyme activity was localized to the paranodal and nodal axolemma. In the reserpinized nerves, reaction product was detectable on the nodal axolemma but was undetectable on the other parts of the axolemma. Nodal K-NPPase was not affected by reserpine treatment. Therefore, the transport Na,K-ATPase on the nodal axolemma might differ from that on the other parts of the axolemma. Allowing reserpinized animals to survive. Two different ouabain-sensitive K-NPPase reactivities, "reserpine-sensitive" and "reserpine-resistant," might be present in the facial nerve of guinea pigs.
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PMID:Cytochemical localization of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase activity in the facial nerve of reserpinized guinea pigs. 926 73

High doses of reserpine induce depletion of biogenic amines. The K-NPPase activity of choroid plexus was determined after one-shot reserpine administration using cerium-based cytochemistry. In normal untreated animals, reaction product was found on the microvilli of the choroidal epithelium but was almost undetectable 3 and 7 days after reserpinization. At 20 days after reserpinization, however, it was detectable. These findings suggested that reserpine decreased the choroidal Na,K-ATPase activity, and that catecholamines might be essential to maintain normal choroidal Na,K-ATPase activity. (J Histochem Cytochem 46: 975-976, 1998)
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PMID:Cytochemical localization of ouabain-sensitive, K+-dependent p-nitrophenylphosphatase activity in the choroid plexus of normal and reserpinized guinea pigs. 967 48

On the basolateral infoldings of the strial marginal cells in the cochlea, Na K ATPase activity is abundant. To clarify the humoral control by norepinephrine, K-NPPase activity of strial marginal cells in the cochlea was investigated in normal, reserpine, norepinephrine (NE), reserpine plus NE-treated guinea pigs using a cerium-based method. K-NPPase activity was almost completely decreased 3-20 days after reserpine administration. At 10 days after reserpinization and following NE repeated treatment, enzyme activity was detectable. These results suggested that norepinephrine might restore and regulate strial K-NPPase activity.
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PMID:Effect of norepinephrine on ouabain-sensitive, K+-dependent p-nitrophenylphosphatase activity in strial marginal cells of the cochlea in normal and reserpinized guinea pigs. 987 Jun 26

In strial marginal cells, Na+/K(+)-ATPase activity is abundant, and contributes to maintain the characteristic electrolyte composition of the cochlear endolymph. In the present study, to clarify the relationship between epinephrine and strial Na+/K(+)-ATPase activity, the ouabain-sensitive, K+-dependent p-nitrophenylphosphatase (K(+)-NPPase) activity of strial marginal cells was investigated with a cerium-based method in normal guinea pigs and guinea pigs treated with reserpine, epinephrine, and reserpine plus epinephrine. In our previous study, K(+)-NPPase activity had almost completely decreased 3 to 20 days after reserpine administration. In the present study, at 10 days after reserpinization and following repeated epinephrine treatment, enzyme activity was detectable. These results suggest that exogenous epinephrine was able to restore strial K(+)-NPPase activity in the reserpine-treated animals, and that epinephrine might increase strial Na+/K(+)-ATPase activity.
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PMID:Effects of epinephrine on ouabain-sensitive, K(+) -dependent P-nitrophenylphosphatase activity in strial marginal cells of guinea pigs. 1021 80

Recent work in animal models of human diffuse axonal injury has generated the hypothesis that, rather than there being physical disruption of the axolemma at the time of injury, a pertubation of the membrane occurs, which leads, over time, to a dysfunction of the physiology of the axolemmal. This dysfunction is posited to lead to a disruption of ionic homeostasis within the injured axon, leading to secondary axotomy some hours after the initial insult. We decided to test the hypothesis that membrane pump/ion channel activity or function is compromised and this would be reflected in structural changes within the axolemma and myelin sheath. We used freeze fracture and cytochemical techniques to provide evidence for change in membrane structure and the activity of membrane pumps after nondisruptive axonal injury in the adult guinea pig optic nerve. Within 10 min of injury, structural changes occurred in the distribution and number of intramembranous particles (IMPs) in the internodal axolemma. By 4 h, there was novel labeling for Ca-ATPase membrane pump activity at the same site. There was loss of IMPs from the nodal axolemma extending over several hours after injury. There was loss of both membrane pump Ca-ATPase and p-nitro-phenylphosphatase (p-NPPase) activity of the node. There was loss of ecto-Ca-ATPase activity but increased labeling for p-NPPase activity at sites of dissociation of compacted myelin. Quantitative freeze-fracture demonstrated statistically significant changes in membrane structure. We provide support for the hypothesis that structural and functional changes occur in the axolemma and myelin sheath at nondisruptive axonal injury.
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PMID:Freeze-fracture and cytochemical evidence for structural and functional alteration in the axolemma and myelin sheath of adult guinea pig optic nerve fibers after stretch injury. 1022 14

PDNP (phosphodiesterase I/nucleotide pyrophosphatase) is one of a series of ectoenzymes that are involved in hydrolysis of extracellular nucleotides. PDNP possesses ATPase (EC 3.6.1.3) and ATP pyrophosphatase (EC 3.6.1.8) activities. Mammalian PDNP consists of three closely related family proteins (PDNP1, -2, and -3), and they are expressed in different cell types and at different developmental stages. Rat PDNP3 is expressed in a subset of immature glial cells and in the alimentary tract. Human PDNP3 is expressed in glioma cells, prostate, and uterus, but not in the alimentary tract. We have cloned genomic DNA containing the whole coding region of the human PDNP3 gene and determined its exon-intron structure. The human PDNP3 gene spans over 60 kb and is organized into 25 exons and 24 introns. We determined the nucleotide sequence of the 5'-flanking region of human and rat PDNP3 genes. The upstream region of both species lacks a canonical TATA box and contains a putative binding site for CCAAT enhancer-binding proteins near the transcription start site. Promoter activity analysis of the 5'-flanking region revealed that the sequence around the CCAAT box is required for its transcriptional activity in 9L rat glioma cells. A gel shift assay demonstrated that 9L nuclear extract contains proteins that bind to this region.
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PMID:Genomic structure and promoter analysis of the ecto-phosphodiesterase I gene (PDNP3) expressed in glial cells. 1052 96

The effect of nantenine, an aporphine alkaloid, on ATPase K+-dependent dephosphorylation was evaluated using p-nitrophenylphosphate (p-NPP) as substrate. Basal K+-p-NPPase activity was significantly increased with 3 x 10(-4) M, remained unchanged with 3 x 10(-6) M, 3 x 10(-5) M but was reduced with 7.5 x 10(-4) M and 1 x 10(-3) M nantenine, whereas Mg2+-p-NPPase activity was not modified. Kinetic studies showed that K+-p-NPPase inhibition by nantenine is competitive to KCl but non-competitive to substrate p-NPP, whereas K+-p-NPPase stimulation by nantenine is non-competitive to KCl but competitive to p-NPP. These data suggest that there may be two acceptor sites for nantenine in p-NPPase, one eliciting stimulation and the other inhibition of K+-dependent p-NPP hydrolysis. Considering the biphasic action of nantenine on seizures and the correlation between decreased ATPase activity and seizure development, alkaloid anticonvulsant effect observed at low nantenine doses is attributable to the stimulation of phosphatase activity whereas the convulsant effect at high alkaloid doses seems related to Na+, K+-ATPase inhibition.
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PMID:In vitro dose dependent inverse effect of nantenine on synaptosomal membrane K+-p-NPPase activity. 1131 51

The physiological action of extracellular ATP and other nucleotides in the nervous system is controlled by surface-located enzymes (ecto-nucleotidases) of which several families with partially overlapping substrate specificities exist. In order to identify ecto-nucleotidases potentially associated with neural cells, we chose PC12 cells for analysis. PC12 cells revealed surface-located ATPase and ADPase activity with apparent K(m)-values of 283 microM and 243 microM, respectively. Using PCR we identified the mRNA of all members of the ecto-nucleoside triphosphate diphosphohydrolase family investigated (NTPDase1 to NTPDase3, NTPDase5/6), of ecto-nucleotide pyrophosphatase/phosphodiesterase3 (NPP3), tissue-non-specific alkaline phosphatase and ecto-5'-nucleotidase. The surface-located catalytic activity differed greatly between the various enzyme species. Our data suggest that hydrolysis of ATP and ADP is mainly due to members of the ecto-nucleoside triphosphate diphosphohydrolase family. Activity of ecto-5'-nucleotidase and alkaline phosphatase was very low and activity of NPP3 was absent. For a detailed analysis of the cellular distribution of ecto-nucleotidases single and double transfections of PC12 cells were performed, followed by fluorescence analysis. Ecto-nucleotidases were distributed over the entire cell surface and accumulated intracellularly in varicosities and neurite tips. PC12 cell ecto-nucleotidases are likely to play an important role in terminating autocrine functions of released nucleotides and in producing extracellular nucleosides supporting the survival and neuritic differentiation of PC12 cells.
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PMID:Multiple ecto-nucleotidases in PC12 cells: identification and cellular distribution after heterologous expression. 1155 76


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