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At least 55 records · Page 3Linked to original sources
PubMed1993

Calcium transport and calcium activated ATPase activity in microsomal vesicles of rat gastric mucosa.

1. Microsomal and plasma membrane vesicles, isolated from rat gastric mucosa, were found to exhibit Ca(2+)-dependent ATPase activities of 14.1 +/- 1.4 and 7.8 +/- 1.1 mumol/mg/hr, respectively. The optimum conditions for the microsomal Ca(2+)-ATPase was pH 6-7, and required Mg2+, while divalent cation such as Cu2+, Zn2+, Fe2+, Ba2+ and Cd2+ had no significant effect. 2. As in the case of Ca2+, Mg(2+)-ATPase, the Ca2+ uptake activity of the microsomal membrane required Mg2+. Both processes were stimulated by submicro molar concentrations of Ca2+ and the apparent Km for Ca2+, Mg2+ ATPase and Ca2+ uptake activities were 0.06 microM and 0.02 microM, respectively. 3. Divalent cations Ba2+ and Fe2+, inhibited both microsomal activities, while Zn2+ and Cd2+ showed no effect on them. However, the monovalent cation K+ did not stimulate Ca2+, Mg(2+)-ATPase and Ca2+ uptake activities. 4. The Ca2+ pumping ATPase of rat gastric mucosal microsome cross-reacted with a monoclonal antibody (mAb-5F10) against the human erythrocyte Ca2+ pump. The apparent molecular weight of mucosal Ca2+ pump was 98 kDa. 5. Close relationship between the kinetic parameters of Ca2+, Mg(2+)-ATPase and Ca2+ uptake activities, and the cross reaction of 98 kDa protein of mucosal microsome with erythrocyte Ca2+ pump antibody, strongly suggest the expression of Ca2+ pump in rat gastric mucosa.

Animals↗
PubMed2005

Fesselin binds to actin and myosin and inhibits actin-activated ATPase activity.

Fesselin is an actin binding protein that bundles actin filaments and accelerates nucleation of actin polymerization. The effect of fesselin on actin polymerization is regulated by Ca(++)-calmodulin. Because actin filaments serve both structural and contractile functions we also examined the effect of fesselin on activation of myosin S1 ATPase activity. Fesselin inhibited the activation of S1-catalyzed ATP hydrolysis in a similar manner in both the presence and absence of tropomyosin. This inhibition was unaffected by Ca(++)-calmodulin. Fesselin inhibited the binding of myosin-S1 to actin during steady-state ATP hydrolysis. Fesselin also displaced caldesmon from actin. S1 displaced fesselin from actin in the absence of nucleotide when the affinity of S1 for actin was much greater than the affinity of fesselin for actin. It is likely that fesselin and S1 share common binding sites on F-actin. We also observed that fesselin could bind to smooth muscle myosin with muM affinity. Fesselin shares some similarities to caldesmon in binding to several other proteins and having multiple potential functions.

Actins↗
PubMedDate not supplied

Calcium-activated ATPase activity in a plasma membrane-rich preparation of rat pancreas.

1. Calcium-stimulated ATPase activity was studied in a plasma membrane rich fraction of rat pancreas homogenate. 2. The enzyme is stimulated to the same maximum rate of ATP hydrolysis by either calcium or magnesium, but the apparent requirement for calcium is five-fold lower than for magnesium. 3. Maximum hydrolytic activity of the enzyme is not increased when additional magnesium is added to the optimal amount of calcium. 4. The enzyme does not require Na+ or K+ for its activation by Ca2+ and is not inhibited by ouabain or 2,4-dinitrophenol. 5. Pancreozymin, in concentrations which evoke secretion of zymogen protein, inhibits the calcium-stimulated ATPase. 6. Carbachol and dibutyryl cyclic AMP, in concentrations which increase the release of digestive proteins, do not alter the activity of the calcium-stimulated enzyme. 7. It is suggested that the plasma membrane calcium-activated enzyme, is not involved in the active calcium extrusion, previously reported to occur with use of the various pancreatic secretagogues tested.

Adenosine Triphosphatases↗
PubMed1979

[Distribution of Mg-activated ATPase activity in the sensorimotor cortex (electron-cytochemical study)].

The localization of Mg-activated ATPase was studied by the lead method. The reaction product was seen in the nuclei and nucleoli of the cells. Five types of its distribution in the nuclei, typical for different types of cells and characterizing their functional activity were distinguished. The reaction to ATPase was also determined in the ribosomes, lipofuscin granules and some oval areas of the cytoplasma of cellular bodies and axons. The precipitate in the brain mitochondria was detected only after the administration of aminazine (15 mg/kg), i. e. in conditions of increased membrane permeability. The presence of ATPase reaction products in axo-dendrite synapses of different types, where it is mainly bound with postsynaptical consolidation and reflects the size of zone activity contacts, may have a direct relation to the conduction of the nervous impulse. The reaction product is also constantly present in the basal membrane of blood vessels.

Adenosine Triphosphatases↗
PubMed1990

Regulation of the actin-activated ATPase activity of Acanthamoeba myosin II by copolymerization with phosphorylated and dephosphorylated peptides derived from the carboxyl-terminal end of the heavy chain.

Myosin II from Acanthamoeba castellanii is a conventional myosin composed of two heavy chains and two pairs of light chains. The amino-terminal approximately 90 kDa of each heavy chain form a globular head that contains the ATPase site and an ATP-sensitive actin-binding site. The carboxyl-terminal approximately 80 kDa of both heavy chains interact to form a coiled coil, helical rod (through which the molecules self-associate into bipolar filaments) ending in a short nonhelical tailpiece. Phosphorylation of 3 serine residues at the tip of the tail (at positions 11, 16, and 21 from the carboxyl terminus) inactivates the actin-activated Mg2(+)-ATPase activity of myosin II filaments. Previous work had indicated that the activity of each myosin II molecule in a filament reflects the global state of phosphorylation of the filament rather than the phosphorylation state of the molecule itself. We have now purified the approximately 28-kDa carboxyl-terminal region of the heavy chain lacking the last two phosphorylation sites, and we have shown that this peptide copolymerizes with and regulates the actin-activated Mg2(+)-ATPase activities of native dephosphorylated and phosphorylated myosin II. It can be concluded from these studies that the biologically relevant enzymatic activity of myosin II is regulated by a phosphorylation-dependent conformational change in the myosin filaments.

Acanthamoeba↗
PubMed1981

Cation fluxes and (Na+ + K+)-activated ATPase activity in erythrocytes of patients with essential hypertension.

Various claims, partially conflicting, have been made in recent years for abnormalities in cation pumps and fluxes in erythrocytes of patients with essential hypertension. In view of the obvious significance of such abnormalities for diagnostic purposes, and possibly for our understanding of the pathophysiology of essential hypertension, we have investigated these claims. We have determined the following parameters of erythrocytes from essential hypertensives and normotensives: 1. (Na+ + K+)-ATPase activity and the Km values for Na+, K+ and ATP; 2. ouabain-sensitive fluxes of Na+ and K+ in Na+-enriched cells after cold treatment and after treatment with p-chloromercuribenzenesulphonate; 3. furosemide-sensitive, ouabain-insensitive cotransport efflux of Na+ + K+. No significant differences were observed, except for a slight decrease in the ouabain-sensitive K+ influx after cold treatment in hypertensives. Hence, we conclude that determination of these parameters in erythrocytes does not seem to be useful for the diagnosis of essential hypertension.

4-Chloromercuribenzenesulfonate↗
PubMed1978

Inhibition of Na+-K+-activated ATPase activity following experimental spinal cord trauma.

The specific activity of the membrane-bound enzyme, Na+-K+-activated adenosine triphosphatase (ATPase), has been shown to be decreased following experimental impact injury (400 gm-cm) to the spinal cord in dogs. The prompt and significant (p less than 0.01) fall in activity was evident as early as 5 minutes after injury, and remained at 56% to 67% of control for the 1-hour period studied. This decrease was most prominent in the central core of the traumatized segments of spinal cord. Central core samples, excised immediately adjacent to the trauma site, gave values for the Na+-K+-activated enzyme intermediate to those of the trauma and control sites. For these same samples, the activity of the Mg+2-dependent ATPase did not change appreciably. No alterations were observed in the tissue surrounding the zone of maximum injury at these early time periods. The relationship of membrane-bound enzyme alterations to blood flow, clotting mechanisms, and abnormal free radical reactions are briefly discussed.

Adenosine Triphosphatases↗
PubMed1977

Na-K-activated ATPase: activity maturation in rabbit nephron segments dissected in vitro.

Single, defined nephron segments were dissected in vitro from fresh slices of neonatal and mature rabbit kidney. Na-K-ATPase was quantified for six different tubule segments with an ultramicromethod. The enzyme distribution pattern in the neonatal nephron was similar to that in the mature nephron. Activity in distal segments was 2-5 times higher than proximal tubule activity referred to tissue dry weight, and 2 times higher referred to tubule length. Neonatal enzyme activity was lower than mature in all segments. Some segments carried only 23% of mature activity. Enzyme activity in the proximal convoluted tubule was constant during maturation when referred to the basal and lateral membrane area measured in the same developmental stages. In vitro activities of these tubules were similar to the enzyme activity measured previously in freeze-dried slices. The Vmax during development of Na-K-ATPase was higher by a factor of 5 in the mature tubule, whereas the Km was identical in the neonatal and mature tubule. The ouabain-insensitive ATPase did not show a maturational activity change.

Adenosine Triphosphatases↗