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Query: UNIPROT:Q3SYG4 (C18)
 23,707 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous investigations have demonstrated an increased amount of a sodium pump inhibitor (N.H.) in plasma from humans with essential hypertension and from animals with various forms of experimental hypertension. The present study has employed Sephadex column and C18 reverse phase separation of urines from patients with essential hypertension and normal controls to distinguish "high", "intermediate" and "low" molecular weight forms of N.H., measured through properties of Na-K-ATPase inhibition and digoxin-like immunoreactivity. The major difference between hypertensive and normotensive urines was a highly significant increase in the "intermediate" molecular weight form of N.H., as measured by Na-K-ATPase inhibition. In contrast, digoxin-like immunoreactivity was significantly decreased in urine from hypertensive patients. The results are compatible with an hypothesis that the defect in some forms of essential hypertension may be partial inhibition of enzymatic conversion of intermediate to final form of N.H., with the increased sodium pump inhibition primarily related to the precursor.
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PMID:Observations on the "cascade" of Na-K-ATPase inhibitory and digoxin-like immunoreactive material in human urine: possible relevance to essential hypertension. 401 67

The artificial insertion of increasing amounts of unsaturated fatty acids into human erythrocyte membranes modulated ATPase activities in a biphasic manner, depending on the number and position of double bonds, their configuration, and the chain length. Uncharged long-chain fatty acid derivatives with double bonds and short-chain fatty acids were ineffective. Stearic acid stimulated Na+ K+-ATPase only. Anionic and non-ionic detergents and alpha-lysophosphatidylcholine failed to stimulate ATPase activities at low, and inhibited them at high concentrations. Mg2+-AtPase activity was maximally enhanced by a factor of 2 in the presence of monoenoic fatty acids; half-maximal stimulation was achieved at a molar ratio of cis(trans)-configurated C18 acids/membrane phospholipid of 0.16 (0.26). Na+K+-ATPase activity was maximally augmented by 20% in the presence of monoenoic C18 fatty acids at 37 degrees C. Half-maximal effects were attained at a molar ratio oleic (elaidic) acid/phospholipid of 0.032 (0.075). Concentrations of free fatty acids which inhibited ATPases activities at 37 degrees C were most stimulatory at reduced temperatures. At 10 degrees C, oleic acid increased Na+K+-ATPase activity fivefold (molar ratio 0.22). Unsaturated fatty acids simulated the effects of calmodulin on Ca2+-ATPase of native erythrocyte membranes (i.e., increase of Vmax from 1.6 to 5 mumol PO43- . phospholipid-1 . hr-1, decrease of K'Ca from 6 microM to 1.4-1.8 microM). Stearic acid decreased K'Ca (2 microM) only, probably due to an increase of negative surface charges. A stimulation of Mg2+-ATPase, Na+K+-ATPase, and Ca2+-ATPase could be achieved by incubation of the membranes with phospholipase A2. An electrostatic segregation of free fatty acids by ATPases with ensuing alterations of surface charge densities and disordering of the hydrophobic environment of the enzymes provides an explanation of the results.
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PMID:Modulation of ATPase activities of human erythrocyte membranes by free fatty acids or phospholipase A2. 612 96

The positions of the double bond and the cis/trans configurations of six mono-unsaturated C18 fatty acids (FA) showed selectivity for inhibition and stimulation of ATPase activities of tissue homogenate fractions. The 13,000 g and 100,000 g sediments (fractions B and C respectively) of tissues homogenates were used as sources of Na+-K+ ATPase and of oligomycin-sensitive (OS) and -insensitive (OIS) Mg2+ ATPase activities. Tissue source included bovine brain and rat brain, kidney, heart and liver. Cis mono-unsaturated C18 FA caused an apparent uncoupling of mitochondrial coupling factor F1 (Mg2+ ATPase). This was indicated by the loss of oligomycin and 1,1,1-trichloro-2,2 bis (p-chlorophenyl) ethane (DDT) sensitivity in the presence of 50 microM FA (12-C18:1). Thus, a precipitous decrease in OS-Mg2+ AtPase activity of mitochondria was accompanied by an equally steep increase in OIS-Mg2+ ATPase activity. This was especially apparent in the heart tissue preparation. The uncoupling action of the FA was not observed with the trans mono-unsaturated C18 FA, Na+-K+ ATPase activity from a bovine brain nerve ending particle (B) fraction was also sensitive to 12-C18:1 FA. However, inhibitory response of Na+-K+ ATPase activity were different for OS-Mg2+ ATPase activity. The latter (OS) was not sensitive to the trans 12-C18:1, while the former (Na+-K+) was sensitive to both cis and trans forms of 12-C18:1 and inhibition appeared to be dependent on the position of the double bond.
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PMID:In vitro response of ATPase activities in tissue subcellular particle preparations to a series of mono-unsaturated C18 fatty acids. 621 Nov 74

Several factors affecting the stimulus-induced vacuolation in cat tracheal submucosal glands described in a companion paper [Am. J. Physiol. 241 (Cell Physiol. 10): C18-C24, 1981] were examined. Stimulation with predominantly alpha-adrenergic, beta-adrenergic, and cholinergic agonists at various concentrations and in the presence of appropriate blockers showed that alpha-adrenergic or cholinergic stimulation is more effective in inducing vacuolation than beta-adrenergic stimulation. In addition, Ca- or HCO3- deficient incubation medium or low incubation temperature either blocked or significantly decreased the vacuolation response. Stimulation in the presence of the Na-K-ATPase inhibitor ouabain prevented vacuolation. The known roles of these factors in fluid transport are consistent with the possibility that stimulus-induced vacuolation possibly arises in response to disturbances in cytoplasmic fluid, which are induced in the secretory cell when the fluid component of secretion is intensely stimulated. A model is presented that possibly relates the observed responses to intracellular event and suggests the possibility of ion pumps in the apical membrane.
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PMID:Possible mechanisms of stimulus-induced vacuolation in serous cells of tracheal secretory glands. 626 3

Arachidonic acid and unsaturated C18 fatty acids at concentrations near 10(-5) M markedly inhibited (H+ + K+)-ATPase in hog or rat gastric membranes. Arachidonic acid was a more potent inhibitor than unsaturated C18 fatty acids, but the involvement of the metabolites of arachidonic acid cascade was ruled out. Linolenic acid inhibited the formation of phosphoenzyme and the K+ -dependent p-nitrophenylphosphatase activity of the hog ATPase. Treatment with fatty acid-free bovine serum albumin abolished only the inhibitory effect of the fatty acid on the phosphatase activity without restoring the overall ATPase action. These data suggest the existence of at least two groups of hydrophobic binding sites in the gastric ATPase for unsaturated long-chain fatty acids which affect differentially the catalytic reactions of the ATPase. (H+ + K+)-ATPase in rat gastric membranes was found more susceptible to the fatty acid inhibition and also more unstable than the ATPase in hog gastric membranes. The presence of a millimolar level of lanthanum chloride or ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid stabilized the rat ATPase probably via the inhibition of Ca2+ -dependent phospholipases in the gastric membranes.
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PMID:Inhibition of gastric (H+ + K+)-ATPase by unsaturated long-chain fatty acids. 629 67

1. The reactivating effect of synthetic analogues of natural lysophosphatidylcholines, acyldeoxyglycerophosphocholines, with acyl chain lengths between C10-C18 on enzymatically delipidated sarcoplasmic membranes has been analyzed. 2. The calcium-dependent ATPase is fully restored by myristoyldeoxyglycerophosphocholine. The restoring effect of deoxyglycerophosphocholines declines when the length of the saturated acyl chain becomes shorter or longer. 3. In contrast to the weakly effective palmitoyldeoxyglycerphosphocholine, its cis-9-mono unsaturated analogue oleyldeoxyglycerophosphocholine proved to be a highly effective reactivating compound. 4. The transfer of the terminal phosphate residue of ATP to the transport protein and the phosphate exchange between ADP and ATP displays the same dependence on the acyl chain length of the deoxyglycerophos-phocholines. In contrast to the ATPase activity the ATP-supported phosphoryltransfer reactions can only partially be restored. 5. A significant restoration of the phosphorylation of the protein by inorganic phosphate could be achieved with none of the deoxyglycerophosphocholines. 6. Below 23 degrees C the apparent activation energy of the calcium-dependent ATPase increases with increasing chain length of the deoxyglycerophosphoclines while above 23 degrees C the activation energies were identical for all restituted preparations.
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PMID:Synthetic monoacylphospholipids as reactivators of the calcium-dependent ATPase of enzymatically delipidated sarcoplasmic membranes. 645 1

The fatty acids palmitic (C16:0), stearic (C18:0), arachidic (C20:0) and arachidonic (C20:4) acids inhibit Ca2+ uptake and enhance Ca2+ efflux measured in vesicles derived from the sarcoplasmic reticulum of skeletal muscle. These effects of the fatty acids are impaired by the Ca(2+)-ATPase ligands Mg2+, Ca2+ and K+, and by drugs that block the leakage of Ca2+ through the Ca(2+)-ATPase such as Ruthenium Red, spermine [de Meis (1991) J. Biol. Chem. 266, 5736-5742] and thapsigargin [de Meis and Inesi (1992) FEBS Lett. 299, 33-35].
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PMID:Modulation by fatty acids of Ca2+ fluxes in sarcoplasmic-reticulum vesicles. 750 58

Two highly purified low-molecular-weight (< 500 Da) Na-K-ATPase inhibitors, one originating from human plasma and the second from human urine, which both eluted in the identical locus from a C18 reversed-phase high-pressure liquid chromatography (HPLC) column, were compared with respect to (a) K effect on Na-K-ATPase inhibition; (b) displacement of [3H]ouabain from binding sites on purified hog brain Na-K-ATPase; (c) cross-reactivity with digoxin antibodies; and (d) vasoconstrictor effects in isolated rabbit femoral arteries. Inhibition of Na-K-ATPase by the plasma factor correlated inversely with K concentration, whereas inhibition by the urine factor correlated directly with K concentration. In the absence of K, the plasma factor displaced [3H]ouabain from both high- and low-affinity binding sites, whereas the urine factor displaced [3H]ouabain only from the low-affinity binding site. Neither factor possessed digoxin-like immunoreactivity. Both factors acted as direct vasoconstrictors, and potentiated the vasoconstrictor action of norepinephrine. The degree of vasoconstriction caused by the plasma factor diminished progressively with added K, indicating that the vasoconstrictor effect of this factor was mediated by the Na-K-ATPase pump. Thus, although both the plasma and urine Na-K-ATPase inhibitors are vasoconstrictors, their mechanisms of action are different.
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PMID:Comparison of low-molecular-weight plasma and urine Na-K-ATPase inhibitors/hypertensive factors. 750 33

The kinetics of the Ca(2+)-ATPase purified from sarcoplasmic reticulum have been studied after reconstitution into bilayers of dimyristoleoylphosphatidylcholine [di(C14:1)PC], dioleoylphosphatidylcholine[di(C18:1)PC] and dinervonylphosphatidylcholine [di(C24:1)PC]. In di(C24:1)PC the rate of phosphorylation of the ATPase by ATP was comparable with that in di(C18:1)PC (about 70 s-1), but in di(C14:1)PC the rate was much lower (21 s-1). Fluorescence responses of the ATPase suggest changes in the phosphoryl-transfer step rather than in the preceding conformational change E1Ca2ATP<-->E1'Ca2ATP. The rate of dephosphorylation of the phosphorylated ATPase was found to decrease in the order di(C24:1)PC < di(C14:1)PC < di(C18:1)PC. For the ATPase in di(C24:1)PC the rate of dephosphorylation (3.3 s-1) was slow enough to be the rate-limiting step for ATP hydrolysis; in di(C14:1)PC, it is suggested that both phosphorylation and dephosphorylation contribute to rate limitation. Phosphorylation of the ATPase in di(C24:1)PC by Pi was normal, but no phosphoenzyme could be detected in di(C14:1)PC. The rate of the Ca(2+)-transport step was normal in di(C24:1)PC, suggesting that the single Ca2+ ion bound to the ATPase in di(C24:1)PC could be transported.
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PMID:Effects of phospholipid fatty acyl chain length on phosphorylation and dephosphorylation of the Ca(2+)-ATPase. 757 21

The characteristics of the interaction between N-(3-pyrene)maleimide (PMI) and the sarcoplasmic reticulum (SR) membranes were investigated, and the sites of labeling with PMI on Ca(2+)-transporting ATPase were identified. PMI was dissolved in the membrane lipids before reacting with the ATPase protein. The measurement of resonance energy transfer from PMI to 1-(dimethylaminophenyl)-6-phenyl-1,3,5-hexatriene revealed that the pyrene moiety of PMI stayed in the lipid layer after it had been covalently attached to the ATPase molecule. PMI-labeled SR membranes at an average labeling density of 1 mol PMI/mol ATPase were digested with trypsin, and the labeled peptides were purified through a series of reversed-phase HPLC procedures on C18 and C4 columns. The amino acid analysis of the purified peptides revealed multiple cysteine residues mainly distributed over the C-terminal half of the cytoplasmic domain of the ATPase molecule as the targets of PMI. This implied that PMI molecules mediated cross-linking between the cytoplasmic domain of the ATPase molecule and the membranes. The distortion of the structure of the former due to this cross-linking may explain the uncoupling of ATP-splitting from Ca(2+)-transport caused by PMI.
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PMID:Sites of labeling with N-(3-pyrene)maleimide on Ca(2+)-transporting ATPase of the sarcoplasmic reticulum. 759 54


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