Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extraction of membrane cholesterol and incorporation of cholesteryl hemisuccinate into the membrane affect the activity of the membrane-bound Mg2+-ATPase. Increasing the ratio of cholesterol to phospholipid from 0.30 mg/mg in the control membranes to 0.45-0.90 in the enriched membranes results in a slight increase of the activity of about 20%. Diminishing the ratio of cholesterol to phospholipid to about one tenth of the ratio of the control membrane results in a decrease of the activity to about 30% of the untreated control. Benzyl alcohol inactivates the membrane-bound enzyme. Digitonin-solubilized Mg2+-ATPase is also inactivated by benzyl alcohol. For concentrations below 20 mM the dependence of the solubilized and the membrane-bound enzymes are virtually identical, and linearly dependent on alcohol concentration. This linear relationship continues up to 70 mM for the solubilized enzyme, while inhibition of the membrane-bound form shows a slightly steeper dependence on inhibitor concentration. It is suggested that the activity of the native Mg2+-ATPase depends on the organization of the lipid phase of the membrane and that addition of benzyl alcohol or depletion of cholesterol results in a disorganization of the lipid phase which in turn results in diminished activity.
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PMID:The effect of changes of the content of membrane cholesterol and the effect of benzyl alcohol on the activity of the intrinsic Mg2+-ATPase from the erythrocyte plasma membrane of the flounder (Platichthys flesus L.). 293 10

The activity of two membrane-bound enzymes of human platelets subjected to DMSO and a freezing-thawing process were analysed. Following treatment of fresh platelets with DMSO (5-20%) quantitative differences of AChE and 'ecto-ATPase' activities were seen. After cryopreservation of platelets in 5% DMSO the enzymatic activities of AChE and Mg2+-ATPase were no different from those obtained for fresh platelets. The lack of any changes in the activities of the enzymes of frozen platelets subjected to a washing procedure to remove DMSO, indicates that the mechanism of the DMSO-induced effect is reversible and that freezing-thawing process had no additional detrimental effects.
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PMID:Effect of DMSO and a freezing-thawing process on the 'ecto-ATPase' and AChE activities of human platelets. 294 81

Rat brain microsomal Mg2+-ATPases with two distinct activities: ethacrynic acid (EA) highly sensitive and EA less sensitive Mg2+-ATPase activities were solubilized by the combined treatment with 10 mM 3-(3-chlolamidopropyl)-dimethylammonio-1-propane-sulfate (CHAPS) and 30 mM octyl-beta-D-glucoside. The solubilized enzymes had properties similar to those of the membrane-bound enzyme in microsomes with respect to the sensitivity to EA and Cl-, although the optimal pH and the affinity to ATP were slightly altered after the solubilization. Fast protein liquid chromatography of the solubilized enzymes on an anion-exchanger (Mono Q) column with a linear NaCl gradient (0-1.0 M) yielded separate peaks for EA highly sensitive and EA less sensitive Mg2+-ATPase activities at 0.1 and 0.35 M NaCl, respectively. Polyacrylamide gradient gel electrophoresis of the samples from the peak-fractions of EA highly sensitive and EA less sensitive Mg2+-ATPase activities yielded prominent bands at 600 and 70 kDa, respectively. These results indicate that EA highly sensitive Mg2+-ATPase is solubilized and separated from EA less sensitive Mg2+-ATPase as a large enzyme molecule with anion-sensitive sites.
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PMID:Solubilization and separation of ethacrynic acid (EA) highly sensitive and EA less sensitive Mg2+-ATPases in the rat brain. 295 25

An estrogen-regulated arginine esteropeptidase is present in the immature rat uterus. The enzymatic complex consists of a membrane-bound activator and a soluble proenzyme. The activator is under strong estrogen control; its activity increases 10-fold 3 h after a single dose of 17 beta-estradiol. The subcellular localization of the activator is determined by a radioactive assay of fractions prepared by sucrose density centrifugation. The distribution of activity parallels the distribution of two plasma membrane markers, Mg2+-ATPase and 5'-nucleotidase. Electron micrographic visualization of the gradient fractions containing the activator reveals a population of vesicles 0.2-0.5 micron in diameter.
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PMID:Estradiol stimulates a uterine plasma membrane protease activator. 296 50

Radiation inactivation technique was employed to measure the functional size of adenosine triphosphatase of spinach chloroplasts. The functional size for acid-base-induced ATP synthesis was 450 +/- 24 kilodaltons; for phenazine methosulfate-mediated ATP synthesis, 613 +/- 33 kilodaltons; and for methanol-activated ATP hydrolysis, 280 +/- 14 kilodaltons. The difference (170 +/- 57 kilodaltons) between 450 +/- 24 and 280 +/- 14 kilodaltons is explained to be the molecular mass of proton channel (coupling factor 0) across the thylakoid membrane. Our data suggest that the stoichiometry of subunits I, II, and III of coupling factor 0 is 1:2:15. Ca2+- and Mg2+-ATPase activated by methanol, heat, and trypsin digestion have a similar functional size. However, anions such as SO3(2-) and CO3(2-) increased the molecular mass for both ATPase's (except trypsin-activated Mg2+-ATPase) by 12-30%. Soluble coupling factor 1 has a larger target size than that of membrane-bound. This is interpreted as the cold effect during irradiation.
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PMID:Radiation inactivation analysis of chloroplast CF0-CF1 ATPase. 296 17

The mechanism of the anaesthetic effect of toluene on the central nervous system (CNS) was studied by using rat erythrocyte and synaptosome membranes as nerve cell models both in vitro and in vivo. The activities of the membrane-bound integral enzymes acetylcholinesterase (AChE), total adenosine triphosphatase (total ATPase) and magnesium-activated adenosine triphosphatase (Mg2+-ATPase) were determined. A short-term exposure to 2000 p.p.m. of toluene had an inhibitory effect on the enzyme activities studied. The degree of inhibition in erythrocyte membranes in vitro and in vivo, and in synaptosome membranes in vitro were in good correlation. In in vivo conditions, the synaptosome-bound enzymes were, however, significantly more inhibited by toluene, which indicates that membranes in vivo are even more vulnerable to the toxic effects of organic solvents than they are as isolated membranes in vitro. However, our results show that in vitro experiments can be used to predict the toxic nerve cell membrane effects of organic solvents. Toluene caused similar enzyme inhibitions both in neural cell membranes and in erythrocyte membranes. Thus, even peripheral non-excitable cell membranes, like erythrocytes, can be used as nerve cell membrane models in studies on the mechanism of the anaesthesia caused by solvents.
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PMID:The effect of in vitro and in vivo toluene exposure on rat erythrocyte and synaptosome membrane integral enzymes. 296 6

Highly purified pig myocardium sarcolemma vesicles possess the Ca2+,Mg2+-ATPase activity (4.1 mumol Pi/mg protein/hour) and induce the ATP-dependent accumulation of 45Ca2+ (6.0 nmol/mg protein/min). This reaction is not stimulated by oxalate; Ca2+ are released from the vesicles by saponin and Na+ treatment, which suggests that Ca2+ transport against the concentration gradient is induced by myocardium sarcolemma vesicles and not by sarcoplasmic reticulum fragments. The phorbol ester possessing a biological activity of a growth-promoting factor and activating membrane-bound protein kinase C stimulates the Ca2+,Mg2+-ATPase activity and the ATP-dependent accumulation of Ca2+, whereas its counterpart devoid of biological activity does not influence Ca2+ transport. Polymixin B, a specific inhibitor of protein kinase C, prevents the activating effect of phorbol esters on Ca2+ accumulation inside the vesicles. It is suggested that the ATP-dependent transport of Ca2+ in myocardium sarcolemma is controlled by Ca2+-phospholipid-dependent phosphorylation catalyzed by protein kinase C.
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PMID:[ATP-dependent transport of Ca2+ in myocardium sarcolemma vesicles and its activation by phorbol esters]. 297 23

A new method using lysophosphatide and acyl-CoA as detergents has been used to solubilize the rat brain opiate receptor. After solubilization, lysophosphatide and acyl-CoA can be almost completely removed by an enzymatic reaction that uses an acyltransferase from rat liver microsomes and reconstitutes the solubilized receptor in membranous vesicles. Morphological studies performed with negative staining and freeze-fracture electron microscopy revealed that the general appearance and intramembrane particle distribution of fracture faces in the reconstituted membrane are similar to those of the native membrane; this indicates that hydrophobic protein components of the original membrane were incorporated during reconstitution. Reconstituted membrane, however, contained higher levels of phosphatidylcholine and lower levels of cholesterol. The activities of the membrane-bound enzymes Na+, K+-ATPase and Ca2+, Mg2+-ATPase in the reconstituted system were 24 and 3%, respectively, those of the native membrane. Although binding of opiate ligands to the reconstituted membrane was stereospecific and saturable, higher concentrations of some of the unlabeled ligands were required to inhibit binding of the radiolabeled ligands. These changes in receptor characteristics are likely due to changes in lipid composition, physical state, and/or distribution of the lipids in the reconstituted membrane bilayer. This conclusion is supported by an increase in the affinity of opiate ligands for reconstituted membrane after adjustment of the latter's lipid composition to match more closely that of the original membrane. This was accomplished by treatment with phospholipid exchange protein to remove the excess phosphatidylcholine and by incorporation of cholesterol into the reconstituted membrane.
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PMID:Enzymatic reconstitution of brain membrane and membrane opiate receptors. 300 99

The distribution of plasma membrane markers, the sodium pump [evaluated as ouabain-sensitive, potassium-stimulated p-nitrophenyl phosphatase (K+-pNPPase)], [3H]saxitoxin binding, and 5'-AMPase, was studied in the subcellular fractions prepared from the homogenates of the longitudinal smooth muscle/myenteric plexus of dog ileum. The K+-pNPPase activity and [3H]-saxitoxin binding were found to be predominantly associated with the synaptosomal fraction as indicated by the high level of these activities in the crude synaptosomal fraction and by the copurification of K+-pNPPase and [3H]saxitoxin binding, but not 5'-AMPase, with several synaptosomal markers during the fractionation of the crude synaptosomal fraction on density gradients. In contrast to the K+-pNPPase activity and [3H]saxitoxin binding, the 5'-AMPase activity was found to be concentrated in the microsomal pellet. Further fractionation of microsomes on density gradient resulted in copurification of 5'-AMPase but not K+-pNPPase or [3H]saxitoxin binding, with other smooth muscle plasma membrane-bound enzymes, such as high-affinity Ca2+-ATPase, Mg2+-ATPase, and Ca2+-ATPase. It was concluded that in the longitudinal smooth muscle/myenteric plexus, the sodium pump activity is present in higher density in the neuronal plasma membranes whereas 5'-AMPase activity is concentrated in the smooth muscle plasma membranes.
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PMID:Subcellular fractionation of the longitudinal smooth muscle/myenteric plexus of dog ileum: dissociation of the distribution of two plasma membrane marker enzymes. 304 Sep 6

Colchicine effect has been tested on rat liver plasma membrane-bound enzymes after in vitro or in vivo treatment. It appears that the in vitro treatment does not affect 5'-nucleotidase, Mg2+-ATPase and (Na+ + K+)-ATPase, whereas adenylate cyclase is sensitive to both in vitro and in vivo treatment, the latter condition being also effective for 5'-nucleotidase.
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PMID:Effect of colchicine on rat liver plasma membrane. 610 80


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