• The Korean Journal of Physiology
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• v.11 no.2
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• pp.1-7
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• 1977

The activity of the $Ca^{++}$ activated adenosinetriphosphatase (Ca-ATPase) of actomyosin systeme of rabbit and frog skeletal muscle has been studied at varying pH and temperature. The PH optima of the Ca-ATPase activity of the rabbit actomyosin was rather broad. Over the temperature range of $16-36^{\circ}C$ activity of the enzyme was not appreciably changed between pH 6.4-8.5; below and above which it rapidly reduced. The pH at the inflection point of the enzyme activity increased as temperature decreased, showing the ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ of approximately $-0.018\;unit/^{\circ}C$. Consequently, $(OH^-)/(H^+)$ ratio at the inflection point was constant regardless of assay temperature. In the frog actomyosin systems the Ca-ATPase activity was not apparently altered between PH 6.4-7.0 when the incubation temperature was $15{\sim}30^{\circ}C$. Outside of this range of pH, however, the enzyme activity was dramatically decreased. The pH of the inflection point changed inversely with temperature. ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ at the acidic side was approximately $-0.018\;unit/^{\circ}C$, whereas that at the alkaline side it was about $-0.037\;unit/^{\circ}C$. The Arrhenius Plot on the Ca-ATPase activity at constant $(OH^-)/(H^+)$ ratio of 1.0 was not linear, but showed break at arround $20^{\circ}C$ for both rabbit and frog actomyosin Preparations. From these results it was speculated that pH dependence of Ca-ATPase activity of rabbit actomyosin systems might reflect titrations of histidine-imidazole and -SH groups, and that of the frog actomyosin represents titrations of histidine-imidazole and lysyllysine ${\alpha}-NH_2$ groups.

• Journal of Bio-Environment Control
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• v.18 no.2
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• pp.160-165
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• 2009

This study was undertaken the effect of high temperature and high humidity on protein expression and especially plasma membrane (PM) $H^{+}ATPase$ of umbel with flowers of early cultivar 'Shinsunhwang' and intermediate cultivar 'Maebsihwang' of onion (Allium cepa L.). There were no visible any difference on the protein pattern from before flowering stage to full flowering stage of two onion cultivars, however, seed set stages were revealed induced/deduced protein patterns. At day 18, protein expression pattern of the high temperature and high humidity treatments of two cultivars was significantly reduced compared to controls. Furthermore, various protein expression of the high temperature treatment was more reduced compared to high humidity treatment. PM $H^{+}ATPase$ expression of the control plants of two onion cultivars was clearly shown, but was not detectable under high temperature treatment of the two onion cultivars using western blot analysis. PM $H^{+}ATPase$ expression of the high humidity treatment was faintly detected intermediate cultivar 'Maebsihwang', not early cultivar 'Shinsunhwang'. These results indicate that protein expression pattern and PM $H^{+}ATPase$ under high temperature treatment was considered to be more damaged compared to high humidity.

• Archives of Pharmacal Research
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• v.16 no.4
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• pp.305-311
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• 1993

$Na^+,K^+$-ATPase activity, $Na^+$-dependent phosphorylation, and $[^3H]$ ouabain binding in sarcolemma prepared from 4 week old spontaneously hypertensive rat(SHR) ventricles were compared to the same parameters in sarcolemma from age matched nomotensive Wister-Kyoto (WKY) rat ventricles to examine whether the reduced myocardial $Na^+$-pump activity in SHR is an inherited enzymatic defect or a second phenomenon due to sustained hypertension. The total body weights, ventricular weights, and blood pressures were the same for SHR and WKY. No significant differences in sarcolemmal protein content and protein recovery were noted between the two groups. Sarcolemma isolated from SHR ventricles showed significantly less $Na^+,K^+$-ATPase activity ande number of phosphorylation sites when compared to sarcolemma from the WKY ventricles. Equilibrium binding of $[^3H]$ouabain and the tumover number of myocardial $Na^+,K^+$-ATPase, however, were the same for both groups. These reults indicate that the low affinity $(\alpha,\;or\;\alpha^1)\;\alpha$ isoform is the same in ventricles of SHR and WKY. The reduced amount of isoform of the $Na^+,K^+$-ATPase inprehypetensive SHR ventricles may play some role in the development of hypertension.

• Archives of Pharmacal Research
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• v.19 no.2
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• pp.126-131
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• 1996

The effects of various synthetic benzimidazole derivatives on gastric H^+/K^+$ATPase activity in vitro were examined. The results showed that the effects of substituents on the benzimidazole ring were not significant. However, replacement of sulfoxide connecting two ring systems to sulfide resulted in a completely inactive compound in vitro, suggesting the essential role of sulfoxide group in the inhibition. In addition, compounds with 5 or 6-membered oxacyclic substituents attached to the pyridine ring displayed the most effective inhibitory activity. Among these derivatives, AU-47 was the most potent, and detailed mechanistic studies with the compound were carried out. AU-47 inhibited gastricH^+/K^+$ATPase in a concentration and time dependent manner with 50% inhibition at $6\muM$. The presence of sulfhydryl reducing agents or substrate analogue protected H^+/K^+$ATPase from the inactivation. The inhibition by AU-47 was potentiated by acid pretreatment of the compound, suggesting the structural conversion of AU-47 into a more active intermediate which was favored in acidic condition. Consistent with in vitro results, AU-47 inhibited in vivo gastric acid secretion. The results suggest that AU47 is a relevant candidate for the development of new antiulcer agent.

• The Korean Journal of Physiology and Pharmacology
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• v.17 no.4
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• pp.275-281
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• 2013

Astrocytes are reported to have critical functions in ischemic brain injury including protective effects against ischemia-induced neuronal dysfunction. Na-K ATPase maintains ionic gradients in astrocytes and is suggested as an indicator of ischemic injury in glial cells. Here, we examined the role of the Na-K ATPase in the pathologic process of ischemic injury of primary cultured astrocytes. Chemical ischemia was induced by sodium azide and glucose deprivation. Lactate dehydrogenase assays showed that the cytotoxic effect of chemical ischemia on astrocytes began to appear at 2 h of ischemia. The expression of Na-K ATPase ${\alpha}1$ subunit protein was increased at 2 h of chemical ischemia and was decreased at 6 h of ischemia, whereas the expression of ${\alpha}1$ subunit mRNA was not changed by chemical ischemia. Na-K ATPase activity was time-dependently decreased at 1, 3, and 6 h of chemical ischemia, whereas the enzyme activity was temporarily recovered to the control value at 2 h of chemical ischemia. Cytotoxicity at 2 h of chemical ischemia was significantly blocked by reoxygenation for 24 h following ischemia. Reoxygenation following chemical ischemia for 1 h significantly increased the activity of the Na-K ATPase, while reoxygenation following ischemia for 2 h slightly decreased the enzyme activity. These results suggest that the critical time for ischemia-induced cytotoxicity of astrocytes might be 2 h after the initiation of ischemic insult and that the increase in the expression and activity of the Na-K ATPase might play a protective role during ischemic injury of astrocytes.

• Journal of Photoscience
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• v.9 no.2
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• pp.335-337
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• 2002

Blue light (BL) induces stomatal opening through activation of H$^{+}$ pump, which creates electrical gradient across the plasma membrane for $K^{+}$ uptake into guard cells. The pump is the plasma membrane H$^{+}$ -ATPase and is activated via phosphorylation of the C-terminus with concomitant binding of the 14-3-3 protein. The opening is initiated by the perception of BL through phototropin (phot), which are recently identified as BL receptors in stomatal guard cells. In this study, we provide the biochemical evidence for phots as BL receptors in stomatal guard cells. vfphot was phosphorylated reversibly by BL, and phosphorylation levels of vfphot increased earlier than those of the plasma membrane W-ATPase. BL-dependent phosphorylations of vfphot and H$^{+}$-ATPase showed similar fluence dependency. Staurosporin, an inhibitor of serine/threonine protein kinase, and diphenyleneiodonium chloride (DPI), an inhibitor of flavoprotein, inhibited BL-dependent phosphorylations of vfphot and H$^{+}$ -ATPase. These results indicate that vfphot acts as a BL-receptor mediating stomatal opening.l opening.

• Animal cells and systems
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• v.8 no.4
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• pp.307-312
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• 2004

Fast kinetics of transient pH changes and difference spectrum formation have been investigated following mixing of ADP/ATP with partially purified plasma membrane PM-ATPase of the pathogenic yeast Candida albicans in the presence of five nutrients: glucose, glutamic acid, proline, lysine, and arginine and two analogs of glucose: 2-deoxy D-glucose and xylose. Average $H^+$- absorption to release ratio, indicative of population of ATPase undergoing complete hydrolytic cycle, was found to be 0.27 for control. This ratio varied between 0.25 (proline) to 0.36 (arginine) for all other compounds tested, except for glucose. In the presence of glucose, $H^+$- absorption to release ratio was exceptionally high (0.92). While no UV difference spectrum was observed with ADP, mixing of ATP with ATPase led to a large conformational change. Exposure to different nutrients restricted the magnitude of the conformational change; the analogs of glucose were found to be ineffective. This suppression was maximal in the case of glucose (80%); with other nutrients, the magnitude of suppression ranged from 40-50%. Rate of $H^+$- absorption, which is indicative of E~P complex dissociation, showed positive correlation with suppression of conformational change only in the case of glucose and no other nutrient/analog. Mode of interaction of glucose with plasma membrane $H^+$-ATPase thus appears to be strikingly distinct compared to that of other nutrients/analogs tested. The results obtained lead us to propose a model for explaining glucose stimulation of plasma membrane $H^+$-ATPase activity.

• Applied Biological Chemistry
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• v.42 no.4
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• pp.298-303
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• 1999

In order to characterize the effects of heavy metal ions on the microsomal ATPase activities, microsomes were prepared from the roots of tomato plant and the activity of microsomal ATPase was measured by an enzyme-coupled assay. $Hg^{2+}$ inhibited the activity of microsomal ATPase in a dose-dependent manner, while $Gd^{3+}$, $Fe^{3+}$, $La^{3+}$, $Zn^{2+}$, and $Pb^{2+}$ inhibited not only the ATPase activity but also the activities of enzymes used in the assay. However, $Cs^+$ and $Ba^{2+}$ showed no significant effect. $Hg^{2+}$ inhibited the activities of both plasma membrane and vacuolar membrane $H^+-ATPases$. In the dose-response to $Hg^{2+}$, the activities of both microsomal $H^+-ATPases$ were severely inhibited at the concentration of $Hg^{2+}$ above $10\;{\mu}M$ and were completely inhibited at 1 mM $Hg^{2+}$. Apparent Ki values of $Hg^{2+}$ on the inhibitions of plasma membrane and vacuolar membrane $H^+-ATPases$ were $80\;{\mu}M$ and $58\;{\mu}M$, respectively. The $Hg^{2+}$-induced inhibitions were reversible since the addition of dithiothreitol completely reversed the inhibitory effects of $Hg^{2+}$. These results suggest that the inhibitory effects of $Hg^{2+}$ on both plasma, membrane and vacuolar membrane $H^+-ATPases$ are nonselective and reversible.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1217-1223
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• 2001

A series of benzimidazole derivatives containing oxycyclic pyridine was prepared and evaluated for their gastric H+ /K+ -ATPase inhibitory activity. Several of the synthesized compound exhibited potent antisecretion in pylorus-ligated rats when administered intradoudenally. Their inhibitory activities were equivalent or comparable to omeprazole.

• The Korean Journal of Physiology
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• v.17 no.2
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• pp.143-159
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• 1983

Vanadate가 가토 신피질절편에서 PAH이동과 Na-K-ATPase활성에 미치는 효과를 관찰한 결과 다음과 같은 결론을 얻었다. 1) Vanadate는 Na-K-ATPase활성을 농도에 따라 억제하였으며 $7.94{\times}10^{-7}M$에서 이 효소의 활성이 50% 억제되었다. 2) Vanadate는 PAH의 능동적이동을 농도에 따라 억제하였으며 50%억제농도는 대략 $10^{-4}M$ 이었고, 수동적이동에는 영향을 미치지 못하였다. 조직내 Na과 K의 양도 vanadate가 PAH이동을 억제하는 농도 범위에서 같이 변화하였고 산소소모량은 $10^{-4}M$까지는 약간 감소하였으나 $10^{-3}M$에서는 오히려 증가하였다. 3) 30분간 preincubation한 후에도 15분까지의 PAH이동은 30분 이후에 비해 vanadate에 의해 적게 억제되었다. 4) $10^{-4}M$ vanadate와 $10^{-4}M$ ouabain은 가역적으로 PAH 이동을 억제하였으며 $10^{-3}M$ vanadate는 비가역적으로 억제하였고 장시간 세척후에도 거의 같은 정도의 억제양상을 나타내었다. 5) Vanadate에 의한 PAH이동의 억제정도는 incubation용액내 $Na^+$의 감소, $K^+$의 증가에 의하여 증가하였고 $Ca^{2+}$의 농도 변화에 의해서는 영향을 받지 않았다. 6) Vanadate가 존재치 않을 때 Tris완충용액 사용시는 pH 8.2까지 PAH축적정도가 증가하였고 phosphate완충용액 사용시는 pH 7.4에서 최대축적치를 보였다. pH가 증가함에 따라 억제정도는 증가하였으며 같은 pH에서도 완충용액의 종류에 따라 vanadate에 의한 억제정도가 달랐다. 7) Vanadate와 ouabain은 PAH이등과 Na-K-ATPase활성에 부가적 억제작용을 나타내었다. 이상의 결과로 vanadate는 가토신장의 세포내부에서 Na-K-ATPase를 가역적으로 억제함으로써 PAH의 이동을 억제하는 것으로 생각되며 PAH의 이동은 Na-K-ATPase활성과 기능적으로 밀접히 연결되어 있는 것으로 생각된다.