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)

Short chain ubiquinones (Q-3) uncouple oxidative phosphorylation in rat heart mitochondria, as shown by polarimetric experiments, and abolish P:O ratios in succinate driven oxidative phosphorylaton. The uncoupling is reversed by long chain ubiquinones (Q-7). Furthermore, short chain ubiquinones abolish oligomycin sensitivity of ATPase; the inhibition is restored by Q-7. The extraction of endogenous ubiquinone from mitochondria reversibly lowers oligomycin sensitivity of ATPase.
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PMID:A role of ubiquinone in energy conservation in mitochondria. 57 43

Cytosolic free Ca2+ rises in pancreatic beta-cells in response to glucose stimulation and is part of the coupling to insulin secretion. This study evaluates a possible role for cytosolic long chain acyl-CoA esters in modulating Ca2+ handling by clonal beta-cells (HIT). Intact cells incubated with 20 microM free palmitic acid exhibited a 40% decrease in basal cytosolic free Ca2+. In contrast, acyl-CoA esters, up to a chain length of 16, but not the corresponding fatty acids, significantly lowered the Ca2+ set point maintained by cells permeabilized with saponin. The maximum response to the various acyl-CoA esters increased with increasing chain length, with no differences in the half-maximally effective concentration of 0.5 microM. Long chain acyl-CoA esters caused a 40-50% increase in 45Ca2+ influx into a non-mitochondrial pool in the permeabilized HIT cells, consistent with a stimulatory effect on the endoplasmic reticulum Ca(2+)-ATPase activity, but did not affect inositol 1,4,5-trisphosphate-induced Ca(2+)-efflux. Thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase activity, blocked the decrease in the Ca2+ set point caused by acyl-CoA esters. The ability of acyl-CoA esters to lower the Ca2+ set point depended on the ATP/ADP ratio (or free ADP); the Ca2+ set point was lowered by 36 +/- 3.6% at an ATP/ADP ratio of 90 and by 14 +/- 1.9% at an ATP/ADP ratio of 7. Depletion of cellular protein kinase C did not prevent the acyl-CoA-induced lowering of the Ca2+ set point. These findings suggest that the increases in long chain acyl-CoA esters may play a role in restoring cytosolic free Ca2+ through activation of Ca(2+)-ATPases.
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PMID:Acyl-CoA esters modulate intracellular Ca2+ handling by permeabilized clonal pancreatic beta-cells. 140 Mar

1. We have used the glycogen-depletion technique, combined with myofibrillar ATPase (mATPase) staining for muscle fibre type, to study the fibre-type composition of four skeleto-fusimotor (beta) units in cat peroneus tertius, namely, one beta dynamic (beta d) unit and three beta static (beta s) units. 2. Depletion of glycogen was observed in serial cross-sections of thirty-four beta-unit extrafusal muscle fibres of various types traced from origin to insertion. No fibre was depleted of glycogen throughout its length; depletion was restricted to a number of zones, usually about five. Oxidative (type I) and oxidative-glycolytic (type IIA) fibres were depleted for a significantly greater proportion of their total length than glycolytic IIB fibres. 3. The fibre-type composition of the beta d unit was determined by tracing its fibres from end to end. The muscle unit consisted of one intrafusal bag1 fibre and ninety-three extrafusal muscle fibres comprising seventy-six type I fibres, eleven IIC fibres, and six fibres that changed from IIC to I during the course of their length (IIC/I fibres). The extrafusal fibre-type composition was thus 81.7% I plus 18.3% IIC and IIC/I. 4. The three beta s units (beta s1, beta s2, beta s3) were all fast-contracting and fatigued rapidly. Identification of their extrafusal fibre types, made in 1 mm2 areas sampled from different parts of each unit, gave mixed compositions as follows: beta s1, IIB + 6.7% IIA; beta s2, IIB + 5.8% IIA; beta s3, IIB + 29.9% IIA. The intrafusal component of each unit included either one or two long chain fibres. 5. In a discussion of the results, the fact that the continuous stimulation of extrafusal muscle fibres does not deplete them of glycogen throughout their length is examined in relation to the work of others who have assumed that it did. With regard to the finding of mixed extrafusal fibre types in the beta units, a distinction is drawn between minimal (around 5%) and moderate mixing. It is suggested that minimal mixing may occur in any motor unit as the outcome of endplate degeneration with foreign replacement, but that moderate mixing indicates an on-going process of conversion from one fibre type to another which in the adult may prove to occur only among beta units.
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PMID:A study of glycogen depletion and the fibre-type composition of cat skeleto-fusimotor units. 143 18

To investigate the vital function(s) of the phosphoinositol-containing sphingolipids of Saccharomyces cerevisiae, we measured their intracellular distribution and found these lipids to be highly localized in the plasma membrane. Sphingolipids were assayed in organelles which had been uniformly labeled with [3H]inositol or 32P and by chemical measurements of alkali-stable lipid P, of long chain bases, and of very long chain fatty acids. We have developed an improved method for the preparation of plasma membranes which is based on the procedure of Duran et al. (Proc. Natl. Acad. Sci. USA 72:3952-3955, 1975). On the basis of marker enzyme and DNA assays carried out with a number of preparations, the plasma membranes contained less than 10% vacuolar membranes (alpha-mannosidase) and nuclei (DNA); the contamination by the endoplasmic reticulum (NADPH-cytochrome c reductase) varied from 0 to 20%. The plasma membrane preparations showed a 13-fold increase in the specific activity of vanadate-sensitive ATPase, compared with that in the homogenate, with a yield ranging from 50 to 80%. A comparison of the distribution of the ATPase with that of sphingolipids assayed by a variety of methods showed that 80 to 100% of the sphingolipids are localized in the plasma membrane; the sphingolipids constitute about 30% of the total phospholipid content of the plasma membrane. Minor amounts of sphingolipids that were found in isolated mitochondria and nuclei can be attributed to the presence of small amounts of plasma membrane in these fractions. These results suggest that one or more essential functions of these lipids is in the plasma membrane. Furthermore, sphingolipids may be useful chemical markers of the plasma membrane of S. cerevisiae.
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PMID:The phosphoinositol sphingolipids of Saccharomyces cerevisiae are highly localized in the plasma membrane. 182 12

Saturated and monounsaturated fatty acids are mainly synthetized in the brain, but some of them could originate from the diet; in contrast polyunsaturated fatty acids are derived from dietary linoleic and linolenic acid. Saturated fatty acid biosynthesis occurs via three main pathways in mammalian cells. One is de novo synthesis of fatty acids from acetyl-CoA via malonyl-CoA; this system has been isolated in soluble form (the soluble system) from various animal tissues including brain. The second and third pathways involve elongation: in the mitochondrial system, acetyl CoA is the principal substrate in extracts from all organs, even brain; in the microsomal system, however, malonyl-CoA acts as donor of the 2 carbon fragments. In vivo studies in brain have shown that very long chain fatty acids are synthesized by elongation rather than by a than by a de novo mechanism. Feeding animals with oils that have a low n-3 acid content (linolenic series) results in all brain cells and organelles reduced amounts of 22:6 n-3 which is compensated for by an increase in 22:5 n-6. The speed of recuperation from these anomalies is extremely slow for brain cells, organelles and microvessels, in contrast with other organs. Essential fatty acids for the brain could be those with very long chains as shown with cell culture. They are probably synthesized in the liver from linolenic acid. They can also be supplied directly by food. During the period of cerebral development there is a linear relation between the n-3 acid content of the brain and that of food until linolenic acid represents approx. 200 mg per 100 g of food (for 1200 mg linoleic acid). A decrease in acids of the linolenic series in the membranes results in a 40% reduction of Na-K-ATPase in nerve terminals and a 20% reduction in 5'-nucleotidase in whole brain homogenate. A diet low in linolenic acid leads to anomalies in the electroretinogram which disappear partially with age, it seriously affects learning tasks. The presence of linolenic acid in the diet confers a greater resistance to certain neurotoxic agents.
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PMID:Control of brain fatty acids. 207 91

In search for a detergent to be used to assess the sidedness of plant plasma membrane vesicles by enzyme latency we tested the effect of 42 detergents on the ATPase activity of right-side-out and inside-out plasma membrane vesicles from sugar beet leaves. Most of the detergents seemed to inactivate the ATPase in addition to disrupting the permeability barrier to ATP. There were two main exceptions, namely long chain polyoxyethylene acyl ethers, such as detergents of the Brij series and Lubrol WX, and long chain lysophospholipids. These two types of detergents permeabilized the membranes at low concentrations and did not inhibit the ATPase at higher concentrations. Unmasking of latent active sites seemed to explain the activation of the plasma membrane H(+)-ATPase produced by long chain polyoxyethylene acyl ethers. These detergents should therefore be ideal for determination of vesicle orientation based on ATPase latency. By contrast, long chain lysophospholipids were found to be highly specific activators of the enzyme. In addition, long chain fatty acids were found to strongly inhibit ATP-dependent proton accumulation in the vesicles without inhibiting ATP hydrolysis. This uncoupling effect of the fatty acids could be abolished by the addition of fatty acid-free bovine serum albumin (BSA). Similarly, the proton transport capacity of ageing vesicles could be restored by addition of BSA. The latter findings may explain why isolated plasma membranes so often exhibit increased permeability to protons on ageing.
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PMID:Effect of detergents on the H(+)-ATPase activity of inside-out and right-side-out plant plasma membrane vesicles. 215 56

Mice were fed diets containing a constant supply of linoleic acid (18:2n-6, LA) as ethyl ester representing 5% by weight of the total fat (5 wt%), in combination with graded amounts of purified docosahexaenoate (22:6n-3, DHA). Cardiac sarcoplasmic reticulum (SR) and mitochondrial phospholipids (PL) from mice fed the diet without DHA contained higher levels of n-6 long chain polyunsaturated fatty acids (PUFA) (22:4n-6 and 22:5n-6) compared to total PL of liver. In the cardiac mitochondrial PL, the level of LA, DHA, the total content of PUFA and the P/S ratio were significantly higher than in SR. A small increase in dietary DHA from 0 to 0.43 wt% induced a 3.6-fold increase in PL DHA content from both cardiac organelles, with a concurrent reduction of n-6 PUFA. The changes in fatty acid PL composition were much more moderate when dietary DHA level was increased to 0.85 and 3.74 wt%. Feeding the lowest amount of DHA resulted in a 6-fold decrease in the value of n-6/n-3 PUFA ratio and a 3.5-fold decrease in the value of 20 carbon chain/22 carbon chain PUFA ratio. DHA was readily depleted from cardiac PL, and only arachidonic acid was retained in the PL from both organelles, after feeding a fat-deficient diet. Despite these drastic modifications in PL fatty acid composition, the maximum velocity (Vm) of SR Ca2+, Mg2+-ATPase was not affected, which indicates that SR cardiac membrane adapts to changes in fatty acid composition to prevent important modifications of its functional properties. However, the Vm of mitochondrial oligomycin-sensitive ATPase was slightly increased in mice fed the lowest amount of DHA. This might be due to an increase in P/S ratio and/or to a modification of cardiolipin fatty acid composition, since this PL is required for optimum function of this enzyme. It is concluded that DHA is strongly taken up by mouse cardiac PL, even in the presence of high dietary LA levels, but its acylation into PL has only little effect on the cardiac ATPase activities.
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PMID:Changes in phospholipid fatty acid composition of mouse cardiac organelles after feeding graded amounts of docosahexaenoate in presence of high levels of linoleate. Effect on cardiac ATPase activities. 252 10

The ability of plasma to inhibit 86 rubidium uptake in rat aorta and to displace [3H]-ouabain from hog brain Na+,K+-ATPase was used as a measure of plasma Na+,K+-ATPase inhibitory activity in seven normotensive and eight hypertensive subjects. Rat aortae rings were incubated in oxygenated plasma containing 86 rubidium (2 microCi/mL) for 30 mins at 37 degrees C and uptake measured and expressed as mumol/kg wet weight/min. Plasma was extracted with a mixture of chloroform and methanol (2:1) and the extract separated by silicic acid column followed by thin layer chromatography and fractions assayed for ouabain displacement using digoxin as a standard. Total ouabain displacement was calculated as the sum of all fractions. There was a strong correlation between the two methods for total plasma Na+,K+-ATPase inhibitory activity (r = 0.761, P less than 0.01). There was a significant positive correlation between plasma Na+,K+-ATPase inhibitory activity and blood pressure in all subjects. Na+,K+-ATPase inhibitory activity was significantly higher in plasma of hypertensives by both methods (P less than 0.001). The increased Na+,K+-ATPase inhibitory activity in plasma from hypertensives was due to the nonesterified fatty acid, long chain acylcarnitine and diphosphatidylglycerol fractions.
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PMID:Higher plasma Na+,K+-ATPase inhibitory activity in essential hypertensive patients. 254 1

We have developed a quantitative and relatively model-independent measure of lipid fluidity using EPR and have applied this method to compare the temperature dependence of lipid hydrocarbon chain fluidity, overall protein rotational mobility, and the calcium-dependent enzymatic activity of the Ca-ATPase in sarcoplasmic reticulum. We define membrane lipid fluidity to be T/eta, where eta is the viscosity of a long chain hydrocarbon reference solvent in which a fatty acid spin label gives the same EPR spectrum (quantitated by the order parameter S) as observed for the same probe in the membrane. This measure is independent of the reference solvent used as long as the spectral line shapes in the membrane and the solvent match precisely, indicating that the same type of anisotropic probe motion occurs in the two systems. We argue that this empirical measurement of fluidity, defined in analogy to the macroscopic fluidity (T/eta) of a bulk solvent, should be more directly related to protein rotational mobility (and thus to protein function) than are more conventional measures of fluidity, such as the rate or amplitude of rotational motion of the lipid hydrocarbon chains themselves. This new definition thus offers a fluidity measure that is more directly relevant to the protein's behavior. The direct relationship between this measure of membrane fluidity and protein rotational mobility is supported by measurements in sarcoplasmic reticulum. The overall rotational motion of the spin-labeled Ca-ATPase protein was measured by saturation-transfer EPR. The Arrhenius activation energy for protein rotational mobility (11-12 kcal/mol/degree) agrees well with the activation energy for lipid fluidity, if defined as in this study, but not if more conventional definitions of lipid fluidity are used. This agreement, which extends over the entire temperature range from 0 to 40 degrees C, suggests that protein mobility depends directly on lipid fluidity in this system, as predicted from hydrodynamic theory. The same activation energy is observed for the calcium-dependent ATPase activity under physiological conditions, suggesting that protein rotational mobility (dependent on lipid fluidity) is involved in the rate-limiting step of active calcium transport.
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PMID:Lipid fluidity directly modulates the overall protein rotational mobility of the Ca-ATPase in sarcoplasmic reticulum. 283 80

Neuronal death generally involves, directly or indirectly, free radical attack and peroxidation. Targets are nucleic acids, proteins, the cytoskeleton, the extracellular matrix and especially membrane polyunsaturated fatty acids. a) One example for the fundamental role of fatty acids. Dietary fatty acids, and more particularly essential polyunsaturated fatty acids, have a direct influence on the composition of cerebral membranes, and hence on their functioning. Each of the two series of polyunsaturated fatty acids plays a particular role. In animals, a deficiency in linolenic acid causes serious perturbations in the nervous system. In fact, feeding animals with oils that have a low n-3 content leads to severe abnormalities in the composition of membranes, both of the brain and other organs. The rate of recovery from these anomalies is extremely slow in the brain, but rapid in the liver. Compared to certain other organs, the nervous system is neither protected against deficiency nor has it priority in the satisfaction if its needs. A decrease in acids of the linolenic series in the membranes results in a 40% reduction of Na-K-ATPase in nerve endings and a 20% reduction in 5'-nucleotidase. It also leads to anomalies in the electroretinogram which disappear with age. This deficiency in linolenic acid has little effect on motor function and disturbes activity and emotivity only slightly, but it seriously affects learning tasks. The presence of linolenic acid in the diet confers greater resistance to certain neurotoxic substances (triethyl lead, for example). Fatty acids essential for the brain could be those with very long chains. They are probably synthesized in the liver from linolenic and linoleic acids. They can also be supplied directly by food. However, if the diet contains a large proportion of very long chain fatty acids (fish oils), the lipid composition of all organs, including the brain, is altered. During the period of brain development there is a linear relation between the polyunsaturated fatty acid content of the brain and that of the diet. The requirement in linolenic acid is 200 mg/100 g of diet (0.4% of calories). That of linoleic acid is 1,200 mg/100 g of diet (2.4% of calories). b) Peroxidation of polyunsaturated fatty acids. Arachidonic acid is released by lysis of phospholipids (it is directly toxic), its peroxidized derivatives are extremely toxic. Peroxidation of membrane lipids alters enzymatic activity, the relationship between receptor and ligand, transport, and the symmetry of the lipid bilayer.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Free radicals, polyunsaturated fatty acids, cell death, brain aging]. 284 29


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