Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Affinity chromatography, using Cibacron blue F3GA bound to Sepharose 4B, and Sephadex G-150 column chromatography, permit the isolation of large quantities of non-esterified cholesterol loaded albumin from rat serum. Unlabeled cholesterol and cholesterol oxides displaced 14C-cholesterol bound to albumin in a dose-dependent manner. Binding of 14C-cholesterol to rat serum albumin in vitro follows a sigmoid curve. Ca2+ ions (up to 10 mM) inhibited the cholesterol binding to albumin in vitro. Fluorescence anisotropy of diphenyl-hexatriene (DPH) embedded in the lipid core of rat brain synaptosomal plasma membranes (SPM) increased with albumin-cholesterol incorporation and decreased in parallel to cholesterol removal. The allosteric properties of the SPM-bound (Na+ + K+)ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by albumin-cholesterol, suggesting that the physical state of the (Na+ + K+)ATPase lipid microenvironment changed from a liquid-crystalline to gel phase. The present studies concerning albumin-cholesterol complex, its behavior and its role in the structure of biomembranes, provide important new clues to the role of this fascinating molecule in normal and pathological states.
 ...
PMID:Effect of rat serum albumin-cholesterol on the physical properties of biomembranes. 282 3

Rat brain homogenates were preincubated with lead chloride for 20 min at 0 degrees C. Inhibition of K-pnitrophenylphosphatase (K-pNPPase), which measures the dephosphorylation step of Na,K-ATPase, reached steady state within 10 min and was readily reversible. The activity in brain, homogenates prepared from 60-day-old rats, expressed (mean +/- SE) as a percentage of control (100.0 +/- 0.48%), fell to 89.4 +/- 0.52% at 0.25 microM [Pb] to 64.2 +/- 1.65% at 5 microM [Pb]. However, between 5 and 25 microM [Pb] K-pNPPase activity significantly increased (to 85.4 +/- 3.14% at 25 microM) before it again fell above 30 microM. Similar results were obtained with brain homogenates prepared from 10-day-old rats. The multiphasic nature of this dose-response curve did not change with changes in buffer, substrate, anion, test tube order, or test tube composition (glass vs plastic), and appeared to be intrinsic to homogenate-Pb interactions. Microsomal preparations also exhibited multiphasicity, but with a shift in the inflection points. However, there was no multiphasicity with commercial hog brain Na,K-ATPase, suggesting an interaction between a component in the rat brain preparations and lead ion. Addition of boiled rat brain homogenate to commercial Na,K-ATPase resulted in partial protection from lead inhibition but did not produce multiphasicity over the ranges tested. Bovine serum albumin provided less protection. We conclude that there is a complex interaction among K-pNPPase activity, some factor in the rat brain homogenate, and low levels of lead ion.
 ...
PMID:Inhibition of brain cation pump enzyme by in vitro lead ion: effects of low level [Pb] and modulation by homogenate. 283 72

The absorption spectrum of visible light, characteristic of the free bilirubin being in the aqueous medium, with a single maximum at 440 nm and with the shoulder in the region of 410-420 nm is transformed into the spectrum with two maxima in the region of 460 and 500 nm, respectively, when the pigment is bound in vitro by the synaptosomal membrane. There are two types of sites for bilirubin binding in the membrane particles, differing in the values of constants of association (Ka = 0.6 . 10(5) and approximately 2.02 . 10(5) M-1, respectively) and in the values of the maximum binding of bilidiene (5.0 and 7.0 nmoles/mg of membrane proteins, respectively). The binding of bilirubin by the synaptosomal membrane leads to a decrease in the specific activity of the membrane Na+,K+-ATPase. The enzyme activity is further decreasing when suspension of the membrane particles is exposed to the blue light (lambda max = 450-460 nm) in the presence of bilirubin. The addition of the serum albumin into the incubation medium potentiates the inhibition effect of bilirubin, when the suspension of membrane particles is lighted in the presence of bilirubin. The alkalization of the medium up to pH 7.8 (from pH 7.2) removes this potentiation effect of the addition of serum albumin.
 ...
PMID:[Effect of bilirubin and serum albumin on the Na,K-ATPase activity in the synaptosomal membrane]. 284 80

The purpose of this study is to evaluate the plasma Na, K-ATPase inhibitor (NKI) in patients with essential hypertension and to compare the mode of its biochemical actions on the Na, K-ATPase with that of ouabain. Plasma NKI was extracted through a reversed-phase cartridge column and its inhibitory action on hog brain Na, K-ATPase was measured in vitro. Plasma NKI activity was significantly greater in patients with essential hypertension (44 +/- 2.8% (S.E.), n = 28, p less than 0.01) than in normotensive controls (25 +/- 2.4%, n = 21). No significant correlation was demonstrated between the values of plasma NKI and mean arterial pressure in either group. Both plasma NKI and ouabain showed a dose-dependent inhibition on the Na, K-ATPase reaction. An action of ouabain was competitively antagonized by increased concentration of potassium in the reaction mixture, while plasma NKI showed a constant inhibition on the Na, K-ATPase independently of potassium concentrations. The action of plasma NKI was of rapid onset and linear with time, while ouabain showed a delayed onset of the reaction over 30 sec, followed by a progressively increasing inhibition on the enzyme reaction. Finally, the inhibitory action of plasma NKI on Na, K-ATPase was completely abolished in the presence of bovine serum albumin even at the concentration of 500 micrograms/ml in the reaction mixture, which did not have any influence on the actions of ouabain. To sum up, the results showed a markedly different nature of plasma NKI from ouabain in the mode of biochemical actions on the Na, K-ATPase in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:A plasma inhibitor of sodium and potassium activated adenosine triphosphatase in patients with essential hypertension. 285 Jun 42

Delipidation of beef heart electron transport particles with phospholipase A2 has been examined. When the particles were treated with the lipase and subjected to a low bovine serum albumin wash, ATPase activity was unaffected as was the lipid/protein ratio of the particles. However, energisation by ATP/Mg2+ was abolished. Furthermore, unsaturated but not saturated fatty acids discharged the steady-state ATP-driven membrane potential of control samples. When the phospholipase A2 hydrolysis products were removed, inhibition of energy-linked reactions in the lipid-depleted particles was still observed and was interpreted in terms of non-specific leaks in the vesicle membranes, and 'specific' leaks through impaired H+-ATPase complexes. ATPase activity was less susceptible to delipidation than energisation but was, nevertheless, strongly inhibited at 50 percent lipid depletion. Spin label studies indicated a decrease in the fluidity of particle membranes accompanying delipidation. Moreover, the discontinuity seen in Arrhenius plots of ATPase activity was shifted from 17 degrees C (control) to 22 degrees C at 50 percent phospholipid depletion. The data are consistent with a release of unsaturated fatty acids by phospholipase A2 rendering the transport particles both leakier and the membranes less fluid than controls.
 ...
PMID:Effects of delipidation on proton translocation and ATPase activity in beef heart electron transport particles. 288 57

The hydrophobic compound diethylstilbestrol inhibits the generation of the proton gradient and the membrane potential in chromatophores from Rhodospirillum rubum and dissipates proton gradients over asolectin vesicle membranes. The Ca2+-ATPase activity of chromatophores, of purified F0F1-ATPase and of purified F1-ATPase is also decreased in the presence of diethylstilbestrol. Other repressed activities are the pyrophosphatase activity of soluble pyrophosphatase from yeast and the NADH oxidation by L-lactate:NAD oxidoreductase. We have previously reported that also ATP synthesis, PPi synthesis and PPi hydrolysis of R. rubrum chromatophores are inhibited by diethylstilbestrol [Strid et al. (1987) Biochim. Biophys. Acta 892, 236-244]. Addition of bovine serum albumin reverses or prevents diethylstilbestrol-induced inhibition of the activities tested. On the other hand, the Mg2+-ATPase activity of chromatophores, purified F0F1-ATPase and purified F1-ATPase are stimulated by low concentrations of diethylstilbestrol. On the basis of its hydrophobicity and the reversal of its inhibition by bovine serum albumin, diethylstilbestrol is proposed to act unspecifically on membranes and at hydrophobic domains of proteins. Such an attack upon the subunits of the F1-ATPase, altering the subunit interactions, is proposed to explain the different results obtained for the Ca2+-ATPase and the Mg2+-ATPase.
 ...
PMID:Diethylstilbestrol. Interactions with membranes and proteins and the different effects upon Ca2+- and Mg2+-dependent activities of the F1-ATPase from Rhodospirillum rubrum. 290 53

The energy requirement for protein breakdown in Escherichia coli appears to be due to protease La, the lon gene product, which hydrolyzes proteins and ATP in a coupled process. This novel enzyme was investigated with small peptides, identified as substrates in the preceding manuscript. Although the degradation of proteins to acid-soluble material requires hydrolysis of a nucleoside triphosphate, cleavage of small fluorogenic substrates, such as glutaryl-Ala-Ala-Phe-methoxynaphthylamine, was found to require only binding of nucleotides to the enzyme. Nonhydrolyzable analogs of ATP, slowly hydrolyzed nucleotides, and even inorganic triphosphate and pyrophosphate stimulate the breakdown of these peptides but not of large proteins such as casein or serum albumin. In addition, vanadate, an inhibitor of the enzyme's ATPase activity, prevents protein degradation, but vanadate does not inhibit and can even stimulate peptide hydrolysis. Degradation of natural oligopeptides or of small polypeptides (less than 10,000 Da) also does not require hydrolysis of the nucleotide. Furthermore, although protein substrates promote ATP cleavage, the fluorogenic peptides inhibit this process. Also, no evidence was obtained for phosphorylation of the protease or of the substrate during ATP hydrolysis. These findings suggest that protein breakdown involves a cyclical series of reactions: 1) ATP binds to the protease and activates it allosterically, thus allowing peptide bond cleavage; 2) the hydrolysis of ATP must occur subsequently and should prevent further peptide bond cleavage until additional nucleoside triphosphates are bound; 3) with proteins as substrates, this reaction cycle probably occurs repeatedly until small peptides are generated.
 ...
PMID:The role of ATP hydrolysis in the breakdown of proteins and peptides by protease La from Escherichia coli. 293 32

The effect of phospholipase A2 on the Ca2+-ATPase (EC 3.6.1.3) activity in the microsomal fraction of rat submandibular gland was kinetically studied in vitro. The Ca2+-ATPase activity was significantly increased by the treatment with phospholipase A2 in the presence of bovine serum albumin as a scavenger for hydrolyzed products. When the microsomal fraction was incubated with phospholipase A2 in the absence of bovine serum albumin, the Ca2+-ATPase activity was not altered. The Vmax and Km values for both ATP and Ca2+ were increased by the phospholipase A2 treatment, respectively. These results indicated that the activation of Ca2+-ATPase by the phospholipase A2 treatment is due to the increase of Vmax.
 ...
PMID:Effect of phospholipase A2 on Ca2+-stimulated adenosine triphosphatase activity in microsomal fraction of rat submandibular gland. 293 55

It is shown that Mg2+, Ca2+-ATPase activity of plasma membrane fragments from the rat small intestine myocytes is inhibited by p-chloromercuribenzoate and dithionitrobenzoate (50 and 90%, respectively). The effect of p-chloromercuribenzoate inhibition is removed by serum albumin promoting a rise in the ATPase activity of the plasma membranes and shifting the temperature maximum point up to 32 degrees C (in the norm the maximum is observed at 36 degrees C). According to the data presented, albumin changes the composition and phase state of the lipid surrounding of the membrane enzymes.
 ...
PMID:[Effect of n-chloromercuribenzoate and albumin on Mg2+, Ca2+-ATPase activity of plasma membranes of smooth muscle cells]. 293 80

A fluorometric micro protein assay based on fluorescamine-labelling of homogeneous proteins in solution has been developed which is capable of accurately quantitating as little as 25 ng protein at a concentration of 1.25 micrograms/ml. This micro assay uses a flow-through HPLC fluorescence detector. Typical micro assays measuring bovine serum albumin standards (0-25 mg/l) yielded linear regression coefficients of r = 0.999. Assays of purified Ca2+-ATPase solutions determined by the micro fluorescamine procedure correlated well with measurements made using the deoxycholate-TCA-precipitation modification of the Lowry assay: 1.0 microgram ATPase by Lowry method = 1.1 microgram protein by fluorescamine microassay (when both procedures were standardized with bovine serum albumin) (r = 0.995). The assay proposed offers a 100-fold increase in sensitivity, compared to the Lowry procedure.
 ...
PMID:Fluorometric determination of nanogram quantities of protein in small samples: application to calcium-transport adenosine triphosphatase. 294 Nov 85


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>