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)

An experiment has been carried out to test the rotating carrier mechanism of the translocation event in membrane transport. To the Ca-ATPase in intact sarcoplasmic reticulum membranes, 2,4-[3H]dinitrophenyl-cadaverine has been covalently attached by the action of the enzyme, transglutaminase. The binding of anti-2,4-dinitrophenyl antibodies to the 2,4-dinitrophenyl-modified membranes was found to have no effect on either the Ca-ATPase activity or the Ca ion transport rate of the membranes. These results rule out the rotating carrier mechanism in this system. A different scheme for the translocation process, the aggregate rearrangement mechanism, is discussed.
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PMID:An experiment eliminating the rotating carrier mechanism for the active transport of Ca ion in sarcoplasmic reticulum membranes. 13 44

The action on muscle proteins of microbial transglutaminase (MTGase), which catalyzes the formation of a "zero-length" covalent cross-link between glutamine and lysine residues in peptides, was studied in order to define a basis for future application of MTGase cross-linking to the study of muscle protein interaction. We examined the cross-linking of skeletal muscle myosin, myosin subfragments, actin, and myofibrils by treatment with MTGase and the possible side-effects of the cross-linking on the enzymic activity of myosin, and found that the rod portions of myosin in myosin filaments were quickly cross-linked to each other by the action of MTGase, but myosin subfragment 1 was not cross-linked to actin. The MgATPase activities at 0.5 M KCl of myosin, heavy meromyosin, subfragment 1, and subfragment 1-actin were not significantly affected by the MTGase reaction. A very small fraction of the head portion of heavy meromyosin was cross-linked to actin in their rigor complexes by MTGase, and the ATPase activity at 0.5 M KCl of the cross-linked heavy meromyosin-actin complexes was slightly enhanced.
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PMID:Cross-linking of contractile proteins from skeletal muscle by treatment with microbial transglutaminase. 135 72

Pentoxifylline, a dimethyl xanthine derivative given to patients with peripheral vascular disorders, increases erythrocyte deformability, diminishes Ca2+ entry, inhibits Ca(2+)-dependent transglutaminase activity and elevates ATP levels. The present study examined the effects of pentoxifylline on the Ca2+ pump ATPase, an enzyme which regulates intracellular Ca2+ levels. Studies were carried out with inside-out vesicles (IOVs) prepared from young (Ey) and old (Eo) human and rat erythrocytes. The pumping of Ca2+ depends on the concomitant hydrolysis of ATP; the two processes were measured using radiolabeled substrates. The catalytic properties of IOVs from young and old erythrocytes were stimulated by pentoxifylline when added directly to the assay medium. Pentoxifylline (0.5 to 5.0 mM) significantly activated the rates of Ca2+ dependent ATP hydrolysis in Ey and Eo IOVs of rat erythrocytes. The percent of activation was greater in the IOVs from older erythrocytes. The Ca2+ translocation was also affected by pentoxifylline. The early burst of Ca2+ uptake into IOVs decreased in the presence of pentoxifylline in Ey IOVs prepared from either species whereas steady state rates of Ca2+ transport only declined at 5.0 mM pentoxifylline. This pattern was not evident in the corresponding Eo IOVs. The response of Ey and Eo IOVs to pentoxifylline may be the basis of the difference in sensitivity of young and old erythrocytes to the drug in regulating intracellular Ca2+ concentrations.
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PMID:The effects of pentoxifylline on the plasma membrane Ca2+ ATPase in age-separated rat and human erythrocytes. 153 32

A proposed mechanism of action of hypoglycemic sulfonylureas is the prevention of transglutaminase-mediated endocytosis of insulin receptors. When activated by high levels of intracellular calcium, transglutaminase (TG) catalyzes the cross-linking of intracellular proteins to membrane proteins and modifies membrane structure and function. This study examined the effects of the sulfonylurea glipizide on TG activity in an erythrocyte model by assessing various membrane ATPase activities and high molecular weight protein polymer formation using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. To activate TG, red blood cells were exposed to 1 mM intracellular Ca2+ using 10(-5) M Ca2(+)-ionophore A23187. In Ca2(+)-stressed cells, calmodulin stimulation (0.1 micrograms/ml) of (Ca2+ + Mg2+)-ATPase was decreased to 21.2% of control activity. Increasing concentrations of calmodulin (0.1-3.0 micrograms/ml) could not overcome the inhibitory effects of TG on the (Ca2+ + Mg2+)-ATPase in Ca2(+)-stressed cells with or without glipizide. An increased Ca2+ sensitivity of calmodulin-independent (Ca2+ + Mg2+)-ATPase due to Ca2+ stress was seen in all Ca2(+)-stressed cells even in the presence of 1 mM glipizide. Structural changes were observed in the form of high molecular weight polymer formation. Cells exposed to high Ca2+ and glipizide (3 x 10(-5)-10(-3) M) showed no improvement in ATPase activity or protection from protein cross-linking compared with cells without the drug. We conclude that in this model glipizide fails to inhibit TG induced protein cross-linking and does not prevent the decrease in (Ca2+ + Mg2+)-ATPase activation in Ca2(+)-stressed red blood cells. This finding considerably weakens the proposal that sulfonylureas act by inhibiting TG activity.
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PMID:Calcium-stressed erythrocyte membrane structure and function for assessing glipizide effects on transglutaminase activation. 167 May 93

A dominant cataract mutation was detected recently among the offspring of x-ray-irradiated male mice. The mutation, which causes total lens opacity, has provisionally been designated by the gene symbol Cat-2t. In the lenses of heterozygous and homozygous Cat-2t mutants, the epithelial and fiber cells were swollen and the lens capsule was ruptured. The histologic analysis demonstrated a complete destruction of the cellular organization of the lens, which might be caused by its altered developmental processes. The data derived from biochemical investigations indicate that biochemistry of the cataractous Cat-2t lenses is affected: the osmotic state as indicated by the increased water content and increased Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity; the energy state as indicated by the decreased adenosine triphosphate (ATP) concentration; and the redox state as indicated by the enhanced content of oxidized glutathione. Additionally, the lenticular protein composition is altered because of the presence of vimentin in the water-soluble fraction. This cannot be explained by the enhanced crosslinking activity of transglutaminase. The changes of the osmotic, energy, and redox states are considered to be secondary in relation to the altered lenticular development. In contrast, the variations concerning vimentin and transglutaminase might be a biochemical indication of the changed development. Possible similarities to other dominantly expressed murine cataract mutants are discussed.
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PMID:Characterization of Cat-2t, a radiation-induced dominant cataract mutation in mice. 197 59

Cataractogenesis was studied in young rats homozygous for the radiation-induced recessive cataract mutation cat. Homozygous cat/cat rats have reduced body weight (about two-thirds of the wild type) when 3 weeks old. The litter size is also diminished to about two-thirds of the wild type. For lens-specific parameters, as compared with homozygous wild type, the wet weight of the cataractous lenses is reduced, although the concentration of water-soluble lens proteins per wet weight is the same. No major alterations could be detected in the pattern of the water-soluble lens proteins separated by isoelectric focusing or gel electrophoresis run with or without mercaptoethanol. Additionally, no statistically significant alterations could be detected in the biochemical parameters of the lens used as indicators for osmotic stress (water content of the lens and the Na+-K+-dependent ATPase), for the energy state (ATP) and for the redox state (oxidized glutathione and superoxide dismutase). In contrast, the activity of transglutaminase is significantly enhanced in lenses as well as in the liver of young cat-rats, which might be understood as a biochemical marker for alterations in the developmental program. Cataractogenesis in the cat-rat is, therefore, suggested to be part of a syndrome including dwarfism and reduced litter size.
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PMID:Biochemical analysis of young rats homozygous for the cataract mutation cat. 256 75

Transglutaminase activity and subcellular distribution have been examined in both normal and tumour tissue. Subcellular fractionation of rat liver demonstrated a bimodial distribution for transglutaminase between the particulate (approximately 40%) and cytosol (approximately 60%) fractions. Isolation of enriched plasma membrane fractions indicated the presence of membrane associated transglutaminase activity which co-distributed with that of 5'-nucleotidase and Na+/K+-ATPase. Induction of hepatocellular carcinomas in rats by treatment with either diethylnitrosamine or 6-p-dimethylaminophenylazobenzothiazole resulted in a reduction in transglutaminase activity which was accompanied by redistribution of the enzyme to the particulate fraction of the cell. The tumour bearing liver appeared to represent an intermediate stage between the hepatocellular carcinoma and control liver when assayed for content and distribution of transglutaminase activity. The transglutaminase activity of four transplantable rat sarcomas (P7, P8, MC3 and CC5) was found to be greatly reduced when compared with the normal tissues of rat liver, lung and spleen. A further reduction in this activity occurred in the primary growths of the sarcomas P7 and P8 following detection of metastases. Our data suggest that such changes in the distribution and content of transglutaminase may be a feature of tumour tissue and may be of value in both monitoring and investigating the carcinogenic process.
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PMID:Alterations in the distribution and activity of transglutaminase during tumour growth and metastasis. 285 74

The data summarized and presented in this paper are consistent with the interpretation that CaM participates in the regulation of the plasma membrane calcium pump. Certain drugs, such as phenothiazines can antagonize CaM. Ca2+ loading of RBCs promotes CaM binding to RBC membranes and results in decreased responsiveness of the [Ca2+ + Mg2+)-ATPase to CaM. The latter effect may be mediated by a Ca2+ activated transglutaminase. Activation of (Ca2+ + Mg2+)-ATPase by CaM in vitro was shown not to be instantaneous, probably because of slow binding. CaM binding to isolated RBC membranes exhibits a Ca2+ dependence that is similar to that for activation of the (Ca2+ + Mg2+)-ATPase, and CaM binding does not decrease at high [Ca2+]s. Calculations based on assumed values for RBC [Ca2+], [CaM], and binding affinities of Ca2+ for CaM and CaM(Ca2+)n for the Ca2+ pump ATPase resulted in the tentative conclusion that most pump sites are occupied by CaM in the RBC in vivo. This conclusion, and the relatively slow time course of the CaM effect on (Ca2+ + Mg2+)-ATPase prompt us to suggest that, for all practical purposes, CaM is a subunit of the Ca2+ pump ATPase in vivo.
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PMID:Calmodulin and the plasma membrane calcium pump. 611 44

Polyamines are natural constituents of most living organisms. However, their function in normal or pathological conditions is not fully understood. We have investigated in vitro effects of polyamines on characteristic properties of isolated renal brush-border membrane vesicles in order to determine whether polyamines have a regulatory role in membrane transport processes. The polyamines putrescine, spermidine and spermine were found to stimulate D-glucose uptake. Diffusional L-glucose uptake was not altered, indicating that the polyamines affected the active transport of D-glucose, rather than inducing nonspecific changes in membrane lipid properties. The amiloride-sensitive Na+ /H + exchange was slightly inhibited by polyamines while Mg2+ -ATPase activity was stimulated. The polyamine effects could not be explained solely by the polycationic properties of these agents, since polycationic polypeptides had an opposite effect. For example, lysozyme was found to inhibit D-glucose transport. Spermine was incorporated into the trichloroacetic acid-insoluble fraction of brush-border membrane proteins. Results indicated that this incorporation process consisted of at least two components: a Ca2+ -independent component and a Ca2+ -dependent component, possibly as a result of transglutaminase activity which was present in the isolated renal brush-border membranes. By using SDS-polyacrylamide gel electrophoresis in conjunction with fluorography, [3H]spermine was shown to be incorporated into several brush-border membrane proteins, mainly the 57 kDa, 74 kDa, 100 kDa, a heavy molecular weight band (greater than 200 kDa) and a low molecular weight band (less than 10 kDa). Our results suggest that the polyamine effects on membrane function may be due to a covalent modification of membrane proteins, possibly via a transglutaminase-mediated incorporation of polyamines or to the crosslinking of membrane proteins.
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PMID:Polyamines stimulate D-glucose transport in isolated renal brush-border membrane vesicles. 614 64

Effect of intraerythrocyte Ca2+ elevation on human and rat erythrocyte membrane (Ca(2+)-Mg2+)-ATPase along with that of incubation of the erythrocyte ghosts in their own hemolysates enriched with Ca2+ has been studied. While the membrane (Ca(2+)-Mg2+)-ATPase levels of Ca(2+)-loaded human erythrocytes showed an initial increase and subsequent decline, membranes incubated in their own hemolysate showed a consistent decrease in the enzyme activity. Calmodulin sensitivity was retained by the preparations in contrast to the earlier observations made with washed erythrocyte membranes. Similar changes in (Ca(2+)-Mg2+)-ATPase activity but of greater magnitude were observed in response to Ca2+ in the calpain-rich rat erythrocytes. Considerable crosslinking and proteolysis was observed in case of human and rat erythrocytes exposed to high Ca2+ concentrations. The Ca(2+)-activable transglutaminase, however, did not play any role in the activation of the (Ca(2+)-Mg2+)-ATPase.
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PMID:Ca(2+)-induced alterations in the activity of membrane (Ca(2+)-Mg2+)-ATPase of human and rat erythrocytes. 835 24


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