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)

A plasma membrane-enriched fraction was prepared from homogenized rat pancreatic islets by a one-step sucrose gradient centrifugation. Using 125I-wheat germ agglutinin as a plasma membrane probe, a fraction was obtained at a sucrose density of about 1.10 that was enriched in 5'-nucleotidase, Mg2+-ATPase and alkaline phosphatase. The fraction contained little, if any, monoamino oxidase activity, insulin or DNA. Hydrolysis of 3-0-methyl-fluoresceinphosphate was stimulated by K+ (10mM) at a pH optimum of pH 8.2. Hydrolysis of ATP-gamma-32P in the presence of MgCl2 was of high specific activity and was optimum at pH 7.0 and 8.2. K+ did not affect ATP-hydrolysis. At pH 8.2, a small fraction of the total Mg2+-ATPase activity was inhibited by ouabain in the presence of Na+ and K+. Since K+-stimulated phosphatase activity does not correlate with Mg2+-ATPase, the two assay systems define separate enzymatic processes.
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PMID:Cation-dependent phosphatase activites in a rat pancreatic islet plasma membrane fraction prepared by one-step gradient centrifugation. 3 53

Concanavalin A inhibits the (Na+-K+)-ATPase activity of isolated rat-liver plasma membranes, while leaving the Mg2+-ATPase unaffected. Glucagon and cyclic AMP act supplementary to the lectin in the inhibition. The lectin effect is counteracted by insulin and L-epinephrine, and is completely abolished by the beta-adrenergic blocking agent propranolol. Results are discussed on the basis of the known interactions of concanavalin A with plasma membrane components, including its hormone-like action.
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PMID:Studies on plasma membranes. XXIII. Hormone-like action of concanavalin A on liver plasma membranes: inhibition of (Na+-K+)ATPase. 12 72

Insulin receptor characteristics were examined in purified brush border membrane from the syncytiotrophoblast of the normal human placenta and quantified during membrane preparation. Insulin receptor concentration was enriched 10- to 15-fold in this preparation, and insulin receptor specific activity followed closely the enrichment values for microvillus plasma membrane markers, alkaline phosphatase, Ca2+- and Mg2+-ATPase, and 5'-nucleotidase during cell fractionation. Insulin receptor concentrations and marker enzyme analyses were compared in whole homogenate, mitochondrial, microsomal, and microvillus fractions, and these fractions were characterized by SDS-gel electrophoresis. Microvillus insulin receptor interactions were dependent on time, [125I]iodoinsulin concentration, protein, and unlabeled hormone concentrations. Competition studies with porcine insulin and [125I]iodoinsulin for this receptor revealed a curvilinear Scatchard plot. Insulinase was demonstrated at 37 C but was minimal at 24 C in the microvillus fraction. Electron microscopy of the microvillus membrane preparation revealed its composition to be mainly spherical closed membrane vesicles and brush border fragments. Sodium dodecyl sulfate polyacrylamide and isoelectric focusing gels of membrane fractions were compared. Actin was tentatively identified as a major microvillus membrane protein and was further fractionated: beta-Actin and gamma-actin were present in approximately equal concentrations. The localization of the insulin receptor in the microvillus brush border of the human placenta suggests that this receptor interacts with maternal, rather than fetal insulin.
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PMID:Characteristics of the microvillus brush border of human placenta: insulin receptor localization in brush border membranes. 75 22

The direct effect of insulin on the high-affinity Ca2+-Mg2+-ATPase was studied in kidney proximal tubular basolateral membranes (BLM) obtained from control and streptozocin-induced non-insulin-dependent diabetes mellitus (NIDDM) rats. Plasma glucose of the diabetic animals was only mildly elevated (217 +/- 9 vs. 138 +/- 3 mg/dl). Both high- and low-affinity calcium-dependent Ca2+-Mg2+-ATPase activities were identified in the BLM. Enzyme activity in BLM from diabetic rats was higher at all Ca2+ concentrations tested due to a higher maximum velocity of the enzyme from NIDDM rats. The high-affinity Ca2+-Mg2+-ATPase activity was inhibited by trifluoroperazine (TFP) in both membranes. No difference in calmodulin content was found in the membranes from the diabetic and control rats. Insulin (16-200 microU/ml) significantly increased the high-affinity Ca2+-Mg2+-ATPase activity (17-40%) in membranes from control animals but had no effect on the enzyme activity in the membranes from the NIDDM rats. The basal activity of the enzyme at 0.1 microM free Ca2+ was higher in the BLM from the NIDDM animals compared to controls (17.8 +/- 0.5 vs. 14.7 +/- 0.8 nM Pi X mg-1 X min-1; P less than .02). There was no effect of insulin on the Ca2+-independent ATPase activity of BLM preparations. These findings demonstrate a defect in the ability of insulin to regulate the high-affinity Ca2+-Mg2+-ATPase activity in BLM from diabetic rats. Such a defect in enzyme activity may play a role in the mechanism of impaired insulin action observed in these NIDDM rats.
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PMID:Ca2+-Mg2+-ATPase activity in kidney basolateral membrane in non-insulin-dependent diabetic rats. Effect of insulin. 294 33

In rats, chronic diabetes is associated with depressed cardiac myosin ATPase activity and a shift from the predominant V1 isoenzyme to V3, correlating with depressed contractility. Rabbit myocardium consists mostly of the V3 isoenzyme, and therefore a switch to even more V3 isoenzyme in diabetes might not be possible and therefore not explain the mechanical abnormalities observed. To explore this, rabbits were made diabetic with 140-150 mg/kg of alloxan, and their hearts were studied 3 days, 1 mo, 3 mo, and 6 mo later. Ca2+-myosin-ATPase activity was decreased in the diabetic rabbit at 1, 3, and 6 mo, correlating with increased percent V3. Actin-activated Mg2+-ATPase activity was not significantly decreased in diabetics, but myofibrillar ATPase activity was decreased in 6-mo diabetic animals. When 3- to 4-mo diabetic animals were administered insulin for 3-4 additional months, myosin-ATPase activity and isoenzyme distribution normalized. These results correlate well with mechanical changes in papillary muscle from these same hearts. They suggest that in rabbit, as in rat, changes in cardiac contractile function are at least partially mediated by changes in myosin isoenzyme composition and are reversible with insulin.
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PMID:Effects of diabetes on cardiac contractile proteins in rabbits and reversal with insulin. 294 66

The ATPase activity of myofibrils and myosin from hindlimb muscle was investigated in animals 4 wk after the induction of diabetes by an intravenous injection of streptozotocin (65 mg/kg). Ca2+-stimulated ATPase in myofibrils was increased in diabetic muscle at various times of incubation (1-7 min) as well as at different concentrations of free Ca2+ (10(-7)-10(-5) M Ca2+). Such an increase in Ca2+-stimulated ATPase was evident as early as 1 wk after streptozotocin injection, but Mg2+-ATPase activity remained unaltered. Treatment of diabetic animals with insulin Ca2+-ATPase and actin-activated ATPase activities of pure myosin were similarly increased in diabetic muscle. Myosin ATPase was also activated by K+- or NH4+-EDTA; these responses were more in diabetic muscle. However, sodium dodecyl sulfate gel electrophoresis failed to reveal differences in the patterns of contractile proteins, and pyrophosphate gels did not show significant changes in myosin isozyme patterns between diabetics and controls. The results of this study demonstrate an activation of contractile protein ATPase of skeletal muscle in diabetes and seem to indicate that such an alteration may be responsible for enhanced contractile function of skeletal muscle in this disease.
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PMID:Altered contractile proteins in skeletal muscle of diabetic rats. 295 57

The levels of the three ATPases found in the erythrocyte membrane of diabetic patients were significantly lower than normal subjects. The distribution of the enzymes was also different. Na+,K+-ATPase and Mg2+-ATPase reflected the status of blood glucose more than Ca2+-ATPase. The ratio between two of the ATPases was sensitive to glycemic response. When dikanut, a viscous preparation, was fed to diabetics for 4 weeks, blood glucose became normal and the activities of the three ATPases increased significantly. The ratio among the enzymes also approached that of normal subjects. A relationship was found between the blood glucose level and erythrocyte membrane ATPases which, if linked to insulin binding or level, may provide a rapid inexpensive assay in diabetes research.
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PMID:Erythrocyte membrane ATPases in diabetes: effect of dikanut (Irvingia gabonensis). 302 98

Na+-K+-dependent ouabain-sensitive ATPase and Mg2+-ATPase have been assayed in the erythrocyte membranes of control subjects and in uncontrolled type I (insulin-dependent) diabetics. A decrease in Na+-K+-ATPase activity was observed in the patients that was significantly correlated with glycemia. The Mg2+-ATPase was increased moderately, and no correlation with glycemia was found. To study the in vivo effect of insulin, ATPase activities were measured in uncontrolled diabetics before and after a 24-h continuous insulin perfusion administered by means of an artificial pancreas. ATPase activities were corrected after normalization of glycemia. It therefore seems that glycemia and/or insulinemia are involved in the regulation of erythrocyte Na+-K+ ouabain-sensitive ATPase and to a lesser extent in that of Mg2+-dependent ATPase.
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PMID:In vivo insulin effect on ATPase activities in erythrocyte membrane from insulin-dependent diabetics. 303 41

Diabetes was induced in rats by an intravenous injection of streptozotocin (65 mg/kg body wt), and animals were killed 8 wk later. Some animals were maintained in a diabetic state for 6 wk and then given 2 wk of insulin treatment in vivo. Myofibrils were isolated and ATPase activities measured. Mg2+-ATPase and Ca2+-stimulated ATPase activities were depressed in diabetic rat hearts in comparison to control; insulin treatment normalized these activities. The depression in myofibrillar ATPases was of gradual onset as no changes were detected 2 wk after inducing diabetes. Treatment of diabetic animals with thyroid hormone did not restore changes in myofibrillar ATPase activities. Marker enzyme activities did not reveal any detectable contamination by cardiac membranes. Mg2+-ATPase activity of myofibrillar preparations from control and diabetic hearts responded differently to N-ethylmaleimide modification. Furthermore, myofibrillar sulfhydryl reactivity to 5,5'-dithiobis(2-nitrobenzoic acid) was significantly depressed in diabetic preparations in comparison to control and insulin-treated diabetic animals. These results suggest that the defect in myofibrillar ATPase activities in chronic diabetes may be due to some modification of sulfhydryl groups.
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PMID:Mechanisms of the defect in cardiac myofibrillar function during diabetes. 315 18

The effect of porcine insulin has been tested in vitro on human erythrocyte plasma membrane (Na+-K+) and Mg2+-ATPase activities as well as on membrane fluidity. The results indicate that the hormonal treatment significantly inhibits (Na+-K+)-ATPase activity, and at the same time decreases membrane fluidity.
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PMID:Insulin effect in vitro on human erythrocyte plasma membrane. 611 62


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