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)

The osteoclast is a highly polarized non-epithelial cell. The apical pole of the cell is determined by the cell's attachment to the extracellular matrix. This attachment forms the sealing zone, delimiting the subosteoclastic bone resorbing compartment. The apical membrane of the cell forms the ruffled-border, which contains some specific membrane proteins and a proton pump ATPase, which acidifies the apical compartment. Newly synthesized lysosomal enzymes are vectorially transported into this apical compartment bound to mannose-6-phosphate receptors. The basolateral membrane is highly enriched in sodium pumps with beta and alpha 1 subunits. Associated with the acidification process is the carbonic anhydrase found in the cytoplasm and membrane-associated and a bicarbonate-chloride exchanger in the membrane.2 These features put the osteoclast in the same functional category as the kidney tubule intercalated cell and the gastric oxyntic cell, both of epithelial origin, which secrete acid in a polarized fashion.
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PMID:Polarity and membrane transport in osteoclasts. 269 52

The ontogeny of lectin-positive epithelial cell types and the maturation of polarized expression of the glycocalyx of the collecting ducts (CD) of the rat kidney were studied from samples of 18th-day fetal and neonatal kidneys of various ages. Lectins from Dolichos biflorus (DBA) and Vicia villosa (VVA), with preferential affinity to principal cells, stained virtually all CD cells of the fetal kidneys. However, within two days postnatally, the number of cells positive for DBA and VVA decreased to amounts found in the adult kidneys. Moreover, a characteristic change occurred rapidly after birth in the intracellular polarization of the reactive glycoconjugates, from a uniform plasmalemmal to a preferentially apical staining. In contrast, lectins from Arachis hypogaea (PNA), Maclura pomifera (MPA) and Lotus tetragonolobus (LTA), reacting indiscriminatively with principal and intercalated cells of adult kidneys, stained most CD cells in the fetal kidneys, and failed to show any postnatal change in the amount of positive cells or in the intracellular polarization. The immunocytochemical tests for (Na + K)-ATPase and carbonic anhydrase (CA II) revealed the characteristic postnatal decrease in the amount of principal cells and simultaneous increase in the amount of CA II rich intercalated cells. DBA and VVA reactive cells also decreased postnatally, paralleling the changes observed in the (Na + K)-ATPase positive principal cells. The present results suggest that the expression of the cell type-specific glycocalyx of principal and intercalated cells is developmentally regulated, undergoes profound changes during maturation, and is most likely associated with electrolyte transport phenomena.
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PMID:Cell type-specific glycoconjugates of collecting duct cells during maturation of the rat kidney. 284 54

The distribution of carbonic anhydrase (CA) and Na+/K+-ATPase was studied histochemically in the pecten of the fowl by light and electron microscopy. No Na+/K+-ATPase activity was seen by the method used here. CA staining was seen in the membranes of the apical and basal microvilli of the endothelial cells, while the cytoplasm took no stain. There were no staining differences between the capillaries of the different regions of the pecten. Only the capillaries of the bridge showed no microvilli and no staining. Neither did arterioles and venules which lacked microvilli stain. The functional significance of the association of CA activity and microvilli is not clear.
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PMID:Histochemical demonstration of carbonic anhydrase and Na+/K+-ATPase in the pecten oculi of the fowl. 284 76

In the search for a functional role for the polarized glycoconjugates of rat collecting duct epithelial cells, the relation between binding of various lectins and expression of cellular transport enzyme profile of the cells was studied. For this purpose, principal and intercalated cells of rat kidney collecting duct were identified by morphological criteria and by their immunocytochemically determined content of (Na+ + K+)-ATPase and carbonic anhydrase (CA II), respectively. Various N-acetylgalactosamine-specific lectins such as those from Helix pomatia and Maclura pomifera revealed heterogeneity among both principal and intercalated cells, whereas alpha-N-acetylgalactosamine-specific lectin from Dolichos biflorus and Vicia villosa bound preferentially to principal cells. Still another lectin from Arachis hypogaea reacted with most collecting duct cells in the cortex and outer medulla, but only with a subpopulation of cells in the inner medulla. Interestingly, some lectins reacted exclusively with the apical aspect of the collecting duct epithelial cells, whereas others revealed both an apical and basolateral distribution of lectin reactive glycoconjugates. The results thus show subtle differences in the glycocalyx structure of principal and intercalated cells and differences in the intracellular polarization of glycoconjugates of these cells. Thus, lectins may be useful tools in the study of the molecular mechanisms which establish and maintain the polarized functions of principal and intercalated cells.
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PMID:Heterogeneity of apical glycoconjugates in kidney collecting ducts: further studies using simultaneous detection of lectin binding sites and immunocytochemical detection of key transport enzymes. 285 98

The generation of focal cortical epilepsy as observed in human partial complex seizures is presumably due to enhanced physiologic responses or paroxysmal depolarization shifts (PDSs). However, the molecular mechanism that underlies these phenomena remains unknown. It could be due to a genetically determined error in a structural or regulatory protein or to posttranslational events that modulate membrane excitability. Since neither neuronal PDSs or interictal EEG spikes are sufficient to produce clinical epilepsy, the clinical expression of epilepsy may need the breakdown of neuronal or glial mechanisms that limit the spread of seizures. Hence, biochemical membrane studies of neurons and glia are necessary to understand the expression of human and experimental epilepsy. This chapter will review the role of glia in controlling neuronal excitability and neuron-glia relationships in experimental and human epilepsy. Data exploring the hypothesis that glial control of extracellular K+ or (K+)o is deficient in focal epilepsy induced by cold lesions will be reviewed. The role of glial carbonic anhydrase (CA) and glial control of putative amino acid transmitters in audiogenic epilepsy will be discussed. In the cold lesion, (K+)o activation constants of synaptosomal (Na+,K+)-ATPase are significantly decreased in the actively firing chronic focus, suggesting that the apparent affinity of the synaptosomal enzyme for K+ was increased within epileptic tissue that was actively firing. Interestingly, while sustained focal paroxysms could raise synaptosomal (Na+,K+)-ATPase, glial (Na+,K+)-ATPase and its activation by (K+)o remained decreased during sustained paroxysms in both acute and chronic lesions. Moreover, while the decrease of the absolute level of glial enzyme activity was less evident 45 days after lesion production, the poor response of glial enzyme to (K+)o never reversed to "normal" values. Hence, these experiments provided new information that glial (Na+,K+)-ATPase responds to K+ in a different manner when compared to synaptic enzyme. Glial ATPase and its activation by (K+)o remain decreased in either actively discharging acute lesions or in the indolent chronic foci. This could mean a reduction in the ability of glial membranes to maintain (K+)o homeostasis. As already suggested by Dichter, the impairment in glial control of elevated (K+)o could be mainly responsible for the transition of interictal discharges to ictal episodes, within the primary and the secondary foci.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Neuron-glia relationships in human and experimental epilepsy: a biochemical point of view. 287 19

Specific antisera were raised against the three carbonic anhydrase (CA) isozymes, CAI, CAII, and CAIII, and were used to determine the fiber distribution of these isozymes in skeletal muscle. Fiber types were determined by ATPase staining, and the CA isozymes were detected using a peroxidase-anti-peroxidase (PAP) technique. All three isozymes were present in type I fibers; CAII and CAIII were exclusive to these fibers, and CAI were also present in some small type 2A fibers.
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PMID:Immunocytochemical localization of carbonic anhydrase isozymes I, II, and III in rat skeletal muscle. 293 98

Sarcoplasmic reticulum vesicles and mitochondria were prepared from red and white skeletal muscles of the rabbit. The preparations were characterized in terms of their specific activities of citrate synthase, basal (Mg2+-dependent) and Ca2+-dependent ATPase (the latter two in the presence of NaN3 and ouabain), and their specific carbonic anhydrase activities were determined. Skeletal muscle mitochondria had high specific activities of citrate synthase (700-1200 mu. mg protein-1) and low carbonic anhydrase activities (0.1-0.4 u. ml mg protein-1). The latter are likely to be due to a contamination of the preparations with sarcoplasmic reticulum (s.r.) Preparations of s.r. vesicles showed negligible activities of citrate synthase and the expected differing patterns of basal and Ca2+-dependent ATPase in red and white muscles. Specific carbonic anhydrase activities in s.r. from both muscle types were high (2-4 u. ml mg protein-1). The highest carbonic anhydrase activity, 11 u. ml mg protein-1, was found in s.r. from rabbit m. masseter. The inhibition constant of s.r. carbonic anhydrase towards acetazolamide was 4-6 X 10(-8) M and similar but not identical to that of cytosolic carbonic anhydrase II. It appears possible that the carbonic anhydrase II-like enzyme previously found by us in muscle homogenates (Siffert & Gros, 1982) originates from the s.r. Histochemical studies using the dansylsuphonamide method described previously (Dermietzel, Leibstein, Siffert, Zamboglou & Gros, 1985) showed an intracellular pattern of carbonic anhydrase staining compatible with the presence of the enzyme in s.r.: spots homogeneously distributed across the fibre cross-sections in transversely sectioned fibres and thin, longitudinally oriented, bands in longitudinally sectioned fibres. It is estimated that s.r. carbonic anhydrase accelerates CO2 hydration within the s.r. approximately 1000-fold. Thus, CO2 and HCO3- react fast enough to provide a rapid source and sink for protons leaving and entering the s.r. in exchange for Ca2+.
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PMID:Carbonic anhydrase in the sarcoplasmic reticulum of rabbit skeletal muscle. 293 36

The role of Ca2+ in the stimulatory action of histamine has been evaluated in the isolated gastric fundus from immature rats, by changing the concentration of calcium ions in the bathing solutions. Lowering Ca2+ to 1.2 mM greatly enhanced the secretory response to histamine, while leaving unaffected that to the H2-receptor agonist, dimaprit. The effect of histamine was competitively antagonized by ranitidine (pA2 = 6.78) in normal solutions; conversely in 1.2 mM Ca2+, the antagonism by ranitidine became unsurmountable. Basal rates of acid secretion did not change in low Ca2+ solutions, whereas they were reduced approximately by 50% in Ca2+-free media. Finally, the secretory response to theophylline was significantly lower in low Ca2+ solutions in comparison with that in control conditions. From the above results it may be concluded that changes in the concentration of Ca2+ ions caused different changes in the secretory response of the rat stomach in the various experimental conditions. The marked enhancement of the response to histamine observed in low Ca2+ is unlikely to be connected with H2-receptors, as suggested by the lack of interference in the response to dimaprit, but it could be related to intracellular mechanisms (H+/K+-ATPase, carbonic anhydrase activation etc.).
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PMID:Effects of Ca2+ ions on gastric acid secretion by the rat isolated stomach. 294 14

This study aimed to investigate the mechanism of active calcium transport in the chick embryonic chorioallantoic membrane (CAM) by assessing the functional involvement of three previously identified, putative components of the transport pathway. These components are a calcium-binding protein (CaBP), Ca2+-activated ATPase and carbonic anhydrase. Using specific reagents, including antibodies and enzyme inhibitors in vivo and in vitro in CAM calcium uptake assays, it was shown that these biochemically identified components were all functionally involved. The results of these studies also indicate that active calcium uptake by the CAM requires the presence of the CaBP on the cell surface in a laterally mobile manner, while carbonic anhydrase appeared to be a cytosolic component. We further analysed the subcellular location of the calcium-uptake activity by gel filtration and density-gradient fractionation of cell-free microsomes of the CAM and the results suggest that this activity is associated with the plasma membrane.
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PMID:Calcium-transport function of the chick embryonic chorioallantoic membrane. II. Functional involvement of calcium-binding protein, Ca2+-ATPase and carbonic anhydrase. 294 5

A method is described for histological localization of carbonic anhydrase (CA) in sections of frozen human muscle using the rapid and inexpensive histochemical technique of Hansson. Results obtained in normal subjects indicate clearly that CA reactive fibers are of type 1. Similarly, abnormalities seen with CA in the muscle biopsy of a patient presenting with type 1 fiber hypotrophy and preponderance duplicated almost exactly those observed with the actinomyosine adenosine triphosphatase and the reduced nicotinamide adenine dinucleotide dehydrogenase reactions. Observations of grouped CA-positive muscle fibers in a case of chronic neurogenic atrophy suggest that, like other enzymes, CA expression in muscle is under neurogenic control.
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PMID:Histochemical localization of carbonic anhydrase in normal and diseased human muscle. 296 57


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