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)

Mg-ATP-dependent 45Ca2+ uptake and Ca2+-ATPase activity have been examined in isolated microsomes obtained by differential centrifugation and in purified subcellular fractions obtained by Ficoll-sucrose density centrifugation in the presence of mitochondrial inhibitors. Mg-ATP-dependent 45Ca2+ uptake increased with increasing EGTA-buffered free [Ca2+], reaching a maximum of 2 nmol 45Ca2+ X 15 min-1 X mg prot-1 at 2 mumol/1 [Ca2+] in the incubation medium. Half-maximal 45Ca2+ uptake was at approximately 0.2 mumol/1 [Ca2+]. Maximal Ca2+ -Mg2+ -ATPase activity was 130 nmol X 15 min-1 X mg prot-1 at 2 mumol/l [Ca2+], with an apparent Km of approximately 0.3 mumol/l [Ca2+]. The Ca2+ ionophore A23187 (10(-6) mol/l), the mercurial compounds mersalyl (10(-5) mol/l) and CH3ClHg (10(-3) mol/l), as well as La3+ (10(-4) mol/l), vanadate (10(-4) mol/l), and saponin (50 micrograms/mg prot), abolished Mg-ATP-promoted 45Ca2+ uptake. In the absence of Mg2+, ATP did not provoke 45Ca2+ uptake. Using the purified smooth membrane fraction (F1) from the Ficoll-sucrose density gradient (enrichment of Na+-K+-ATPase specific activity by ninefold and of NADH-cytochrome c reductase by threefold as compared with total tissue homogenate), Mg-ATP-dependent 45Ca2+ uptake correlated better with Na+-K+-ATPase (r = 0.97) than with the smooth endoplasmic marker NADH-cytochrome c reductase (r = 0.52). No correlation was found with RNA, the marker for rough endoplasmic reticulum. We conclude that pancreatic plasma membranes contain a Ca2+-Mg2+-ATPase that represents the Ca2+ extrusion system from acinar cells. It is also possible that vesicular membrane structures associated with the plasma membrane, or endocytotic plasma membrane vesicles, take up Ca2+ and represent an intracellular Ca2+ pool.
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PMID:Characterization of Mg-ATP-dependent Ca2+ transport in cat pancreatic microsomes. 613 52

Administration of lindane at a dose of 20 mg/kg body weight/day for 15 days to male rats brought about marked growth retardation. Succinic dehydrogenase, Mg2+-ATPase and glucose-6-phosphatase activities were inhibited in different fractions of liver tissues. Mg2+-ATPase, alkaline phosphatase and NADH-dehydrogenase activities were also inhibited in the liver plasma membranes of the lindane treated animals. Stimulation of 5'-nucleotidase activity in liver plasma membrane was observed under lindane intoxication. Supplementation of L-ascorbic acid by separate oral administration to the lindane intoxicated rats neutralized the growth retardation and maintained almost normal values of all the enzymes studied.
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PMID:Protective effect of L-ascorbic acid in lindane intoxicated rats. 618 53

Vanadate is a potent inhibitor of Na+,K+-ATPase derived from bovine aorta. The Ca2+, Mg2+-ATPase of the same preparation was inhibited at 10 times higher concentrations. Compared with [3H]ouabain, 48V bound quickly to bovine aortic microsomes. Equilibrium binding experiments revealed one high-affinity, low-capacity and one low-affinity binding site for 48V, whereas [3H]ouabain possessed only one binding site of high affinity. A high NADH-vanadate reductase activity was measured in the same preparation, suggesting that, in this tissue, vanadate may be converted to vanadyl, a form to which the Na+,K+-ATPase is relatively insensitive. An increase in the contractile force of isolated rabbit aorta was measured with the following potency: phenylephrine greater than ouabain greater than vanadate. The order in intrinsic activity was as follows: phenylephrine congruent to ouabain greater than vanadate. The action of vanadate was rapid in onset and stable over several hours, while that of ouabain was slow and transitory. Vanadate increased tension in isolated rabbit veins to an extent similar to phenylephrine, but at concentrations two orders of magnitude higher. Vanadate action decreased with decreasing (Ca2+)0, but remained constant at a constant ratio of (Ca2+)0/(Na+)2(0). Vanadate-induced increases in tension were decreased by verapamil by about 43% and persisted in a solution in which Na+ was replaced by Li+. Vanadate increased electrically stimulated contractions. It is concluded that most of the effect of vanadate is due to an increase in calcium influx into the smooth muscle cell and that the effect of vanadate on Na+,Ca2+ exchange is of minor importance.
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PMID:Effects of vanadate on isolated vascular tissue: biochemical and functional investigations. 618 8

We recently reported that the phospholipid composition of mouse liver microsomes could be altered in vivo by a combination of dietary choline deprivation and administration of the methylation inhibitors periodate-oxidized adenosine and cycloleucine (D.M. Boyle & W.L. Dean (1982) Biochim. Biophys. Acta 688, 667-670). We have now determined the effect of this in vivo change in phospholipid composition on 7 microsomal enzyme activities and 2 cytochromes. The specific contents of cytochromes b5 and P-450 were unaffected by the treatment. Similarly, NADH-cytochrome c reductase, cytochrome P-450 reductase, cyclohexane hydroxylase and Mg2+-ATPase were not significantly altered. In addition, the phospholipid/protein ratio was not changed. In contrast, Ca2+-ATPase and Ca2+ transport rates were reduced by more than 60%. This result suggests that the mouse liver microsomal Ca2+-ATPase is extremely sensitive to the phospholipid composition of the membrane in which it is embedded and that one mode of control of calcium metabolism in liver cells could be at the level of membrane phospholipid composition.
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PMID:Effect of in vivo changes in phospholipid composition on liver microsomal calcium transport. 624 Mar 18

Lantana camara caused, in guinea pigs, a decrease in hepatic mitochondrial protein content. The phospholipid to protein ratio did not change but there was a marked increase in the cholesterol to protein ratio and the cholesterol to phospholipid ratio. Enzyme activities of succinic dehydrogenase, glutamate dehydrogenase, cytochrome oxidase and Mg2+-ATPase increased, while the activity of NADH-ferricyanide reductase remained unaffected. Mitochondrial swelling, in the absence or presence of ascorbic acid, decreased in hepatic mitochondria from lantana-intoxicated guinea pigs.
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PMID:Biochemical effects of the plant Lantana camara on guinea pig liver mitochondria. 713 17


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