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

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently reported that autophosphorylated protein kinase C (PKC) has an intrinsic Ca(2+)- and phospholipid-dependent ATPase activity and that the ATPase and histone kinase activities of PKC have similar metal-ion cofactor requirements and Km,app(ATP) values. We hypothesized that the intrinsic ATPase activity of PKC may represent the bond-breaking step of its protein kinase activity. The rate of the ATPase reaction is several times slower than the histone kinase reaction rate. At subsaturating concentrations, various peptide and protein substrates stimulate the ATPase reaction by as much as 1.5-fold. In contrast, non-phosphorylatable substrate analogs are not stimulatory. These observations support a mechanism of PKC catalysis in which the productive binding of phosphoacceptor substrates enhances the rate of phosphodonor substrate (ATP) hydrolysis at the active site of PKC. However, this mechanism contains an assumption that the ATPase activity of PKC is catalyzed at the active site. In fact, sequence analysis indicates that PKC contains a potential second nucleotide binding site outside of its active site. In this report, we provide a detailed analysis of the relationship between the active site of PKC and the intrinsic ATPase activity of the enzyme. We show that the regulatory and catalytic properties of the ATPase reactions of three PKC isozymes are similar, despite critical differences among the isozymes in their consensus sequences for the potential non-active-site nucleotide binding site in their catalytic domains. We also show that the ATPase and histone kinase reactions of each isozyme have similar Km,app(ATP) values.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:The intrinsic ATPase activity of protein kinase C is catalyzed at the active site of the enzyme. 153 19

The impaired Na(+)-K(+)-ATPase activity in peripheral nerve from diabetic rats is prevented by dietary myo-inositol (MI) supplementation in vivo and corrected by protein kinase C (PKC) agonists in vitro, suggesting that PKC may mediate the effects of nerve MI depletion on Na(+)-K(+)-ATPase activity. However, little is known about the effect of diabetes on PKC activity or peptide in rat peripheral nerve. Therefore, the effect of streptozocin-induced diabetes and dietary MI supplementation on the activity and distribution of PKC in rat sciatic nerve homogenates and cytosolic and particulate fractions was explored with histone phosphorylation assay and Western-blot analysis. PKC activity but not peptide was selectively decreased in the cytosolic fraction by streptozocin-induced diabetes, and this abnormality was partially corrected by dietary MI supplementation. These results suggest that altered MI metabolism may affect nerve PKC specific activity, and this alteration may play a role in reduced Na(+)-K(+)-ATPase activity and blunted regenerative response in diabetic nerve.
...
PMID:Diminished specific activity of cytosolic protein kinase C in sciatic nerve of streptozocin-induced diabetic rats and its correction by dietary myo-inositol. 165 70

Interactions of certain naturally occurring, amphiphilic polypeptides with membranes were investigated. Mastoparan (wasp venom toxin), melittin (bee venom toxin), cardiotoxin (cobra venom toxin), and polymyxin B (antibacterial antibiotic) inhibited protein kinase C stimulated by phosphatidylserine bilayer or arachidonate monomer and blocked binding of [3H] phorbol 12,13-dibutyrate to protein kinase C in the presence of phosphatidylserine bilayer, with IC50 values (concentrations causing 50% inhibition) of 1-8 microM. Mastoparan and polymyxin B were much less inhibitory (IC50, 10-20 microM), whereas melittin and cardiotoxin were similarly inhibitory (IC50, 1-4 microM), when protein kinase C was activated instead by synaptosomal membrane. Kinetic analysis indicate that mastoparan inhibited protein kinase C, assayed using phosphatidylserine or synaptosomal membrane as the phospholipid cofactor, competitively with the phospholipid cofactor, in a mixed manner with CaCl2 or diacylglycerol, noncompetitively with histone, and uncompetitively with ATP, with apparent Ki values of 1.6-18.7 microM. Inhibition of Na,K-ATPase in the membrane by these polypeptides had relative potencies different from those for their inhibition of protein kinase C activated by the same membrane preparation; mastoparan and melittin inhibited the two activities with comparable potencies, but polymyxin B and cardiotoxin were far less effective in inhibiting Na,K-ATPase. The same relative inhibitory potencies of the polypeptides (melittin greater than mastoparan greater than polymyxin B) for inhibition of Na,K-ATPase were also noted for their inhibition of Ca2+/calmodulin-dependent protein kinase II, 86Rb uptake (Na+ pump) by HL60 cells and the phorbol ester-induced differentiation of the leukemia cells. These findings were consistent with discrete interactions of the polypeptides with functionally distinct sites on the membrane, leading to differential inhibition of biological activities associated with the membrane. Actions of certain polypeptides appeared to be more specific compared to those of lipid second messengers such as lyso-phosphatidylcholine and sphingosine, and the antineoplastic ether lipid analogs such as 1-O-octadecyl-2-methyl-rac-glycero-3-ophosphocholine.
...
PMID:Membrane interactions of amphiphilic polypeptides mastoparan, melittin, polymyxin B, and cardiotoxin. Differential inhibition of protein kinase C, Ca2+/calmodulin-dependent protein kinase II and synaptosomal membrane Na,K-ATPase, and Na+ pump and differentiation of HL60 cells. 184 32

We recently reported that autophosphorylated rat brain protein kinase C (PKC) catalyzes a Ca2(+)- and phosphatidylserine- (PS-) dependent ATPase reaction. The Ca2(+)- and PS-dependent ATPase and histone kinase reactions of PKC each had a Km app(ATP) of 6 microM. Remarkably, the catalytic fragment of PKC lacked detectable ATPase activity. In this paper, we show that subsaturating concentrations of protein substrates accelerate the ATPase reaction catalyzed by PKC and that protein and peptide substrates of PKC induce ATPase catalysis by the catalytic fragment. At subsaturating concentrations, histone III-S and protamine sulfate each accelerated the ATPase activity of PKC in the presence of Ca2+ and PS by as much as 1.5-fold. At saturating concentrations, the protein substrates were inhibitory. Poly(L-lysine) failed to accelerate the ATPase activity, indicating that the acceleration observed with histone III-S and protamine sulfate was not simply a result of their gross physical properties. Furthermore, histone III-S induced the ATPase activity of the catalytic fragment of PKC, at both subsaturating and saturating histone concentrations. The induction of ATPase activity was also elicited by the peptide substrate Arg-Arg-Lys-Ala-Ser-Gly-Pro-Pro-Val, when the peptide was present at concentrations near its Km app. The induction of the ATPase activity by the nonapeptide provides strong evidence that the binding of phospho acceptor substrates to the active site of PKC can stimulate ATP hydrolysis. Taken together, our results indicate that PKC-catalyzed protein phosphorylation is inefficient, since it is accompanied by Pi production.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Stimulation of the ATPase activity of rat brain protein kinase C by phospho acceptor substrates of the enzyme. 184 1

Protein kinase C (PKC) consists of a family of Ca2(+)- and phospholipid-dependent protein kinases that catalyze the transfer of the gamma-phosphate of ATP to phosphoacceptor serine or threonine residues of protein and peptide substrates. In this report, we demonstrate that purified, autophosphorylated rat brain PKC catalyzes a Ca2(+)- and phospholipid-dependent ATPase reaction, that appears to represent the bond-breaking step of its phosphotransferase reaction. The histone kinase and ATPase activities of PKC each had a Kmapp of 6 microM for ATP, and their metal ion cofactor requirements were similar. The rate of the Ca2(+)- and phospholipid-dependent PKC-catalyzed ATPase reaction was approximately 5 times slower than the rate of histone phosphorylation, but the basal rates of the PKC-catalyzed ATPase and histone kinase activities differed by less than a factor of 2. The mechanism of the ATPase reaction could entail either direct hydrolysis of ATP by water or formation of a stable phosphoenzyme (PKC-P) followed by its hydrolysis (PKC + Pi). The latter mechanism appears unlikely since [gamma-32P]ATP failed to label autophosphorylated PKC. Furthermore, the PKC preparation did not contain contaminating protein phosphatases, excluding the possibility that the ATPase activity represented dephosphorylation of contaminating PKC substrates. Therefore, our results suggest that water may effectively compete with protein substrates of PKC for the gamma-phosphate of ATP. Using PKC inhibitors and activators, we found that the ATPase and protein kinase activities of PKC were regulated analogously, providing evidence that allosteric activation of PKC involves facilitation of the bond-breaking step of the phosphotransferase reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Characterization of a Ca2(+)- and phospholipid-dependent ATPase reaction catalyzed by rat brain protein kinase C. 216 79

Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in canine cardiac microsomes were found to be stimulated by heparin and various other polyanions. Prior treatment of the microsomes with the ionophores alamethicin or A23187 produced no change in the extent of stimulation of the ATPase activity by heparin yet eliminated net calcium uptake. This finding and a lack of change in the stoichiometric ratio of mol of calcium transported/mol of ATP hydrolyzed (calcium:ATP) suggest that the effect of heparin is on the calcium pump rather than on a parallel calcium efflux pathway. Certain polycationic compounds including poly-L-arginine and histone inhibited both cardiac and fast skeletal muscle microsomal calcium uptake and also produced no change in the stoichiometric ratio of calcium to ATP. Several lines of evidence indicate that the polyanionic compounds tested stimulate calcium uptake by interacting with phospholamban, the putative phosphorylatable regulator of the cardiac sarcoplasmic reticulum calcium pump, whereas polycationic compounds appear to interact with the pump. (i) Heparin stimulated calcium uptake to the same extent as protein kinase A or trypsin, whereas prior phosphorylation or tryptic cleavage of phospholamban from the membrane abolished the stimulatory effect of heparin. (ii) Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in fast skeletal muscle microsomes, which lack phospholamban, were unaffected by heparin. (iii) Purified cardiac (Ca2+ + Mg2+)-ATPase activity was no longer stimulated by heparin yet was still inhibited by polycationic compounds. The heparin-induced stimulation of calcium uptake was dependent on the pH and ionic strength of the heparin-containing preincubation medium, hence electrostatic interactions appear to play a significant role in heparin's stimulatory action. The data are consistent with an inhibitory role of the positively charged cytoplasmic domain of phospholamban with respect to calcium pump activity and the relief of the inhibition upon reduction in phospholamban's positive charge by phosphorylation or binding of polyanions.
...
PMID:Modulation by polyelectrolytes of canine cardiac microsomal calcium uptake and the possible relationship to phospholamban. 247 44

ATP-promoted efflux of poly(A)-rich RNA from isolated nuclei of prelabeled mouse lymphoma L5178y cells has an activation energy of 51.5 kJ/mol, similar to that found for the nuclear envelope nucleoside triphosphatase (48.1 kJ/mol) assumed to be involved in mediating nucleocytoplasmic transport of at least some RNA. Here we show that efflux of two specific poly(A)-rich mRNAs (actin and beta-tubulin) from isolated L-cell nuclei is almost totally dependent on the presence of ATP, while efflux of poly(A)-free histone mRNA (H4, H2B, and H1) also occurs to a marked extent in the absence of this nucleotide. Measurements of temperature dependence of transport rate revealed an activation energy of 56.1 kJ/mol for actin mRNA, while the activation energy for histone-H4-mRNA efflux was in the same range as that found for ATP-induced release of RNA from demembranated nuclei (about 15-20 kJ/mol). Addition of nonhydrolyzable nucleotide analogs of ATP to the in vitro system used for measurement of RNA transport did not result in release of nonhistone mRNA (actin), but enhanced the efflux of H4 mRNA to approximately the same extent as ATP. Although not absolutely required, addition of ATP stimulated the rate of export of histone mRNA about twofold. Only the poly(A)-rich RNA, but not the poly(A)-free RNA, released from isolated nuclei was found to compete with poly(A) for the nuclear envelope mRNA-binding site, indicating the mechanism of transport for both RNA classes to be distinct. Export of both nonhistone and histone mRNA was found to be inhibited by a monoclonal antibody against a p60 nuclear-pore-complex antigen. This antibody had no effect on the nucleoside triphosphatase, mediating transport of poly(A)-rich mRNA.
...
PMID:Energy requirement and kinetics of transport of poly(A)-free histone mRNA compared to poly(A)-rich mRNA from isolated L-cell nuclei. 256 12

Six weeks after induction of diabetes, the rate of ouabain-sensitive 86Rb+ accumulation, a parameter which reflects Na+ + K+-ATPase pumping activity, was significantly reduced in endoneurial preparations of sciatic nerve from untreated diabetic rats compared with that in control rats (Trial, 1, 0.19 +/- 0.09 versus 0.48 +/- 0.13 pmol/min per mg wet weight of tissue, p less than 0.001; Trial 2, 0.27 +/- 0.16 versus 0.47 +/- 0.18, p less than 0.01). This decrease in ouabain-sensitive 86Rb+ uptake was not observed in nerves from diabetic rats maintained on sorbinil (an aldose reductase inhibitor) or myo-inositol diets. Protein kinase C activity was demonstrated in the soluble fraction of a sciatic nerve homogenate by assaying for lipid-activated, Ca+-dependent phosphorylation of calf thymus histone. No significant difference in the time course of kinase C activity was observed between cytosol fractions of nerve homogenates from control and diabetic rats (control, 6.22 +/- 0.97 pmol 32P incorporated/mg cytosol protein in 50 min; diabetic, 5.32 +/- 0.71). Three low molecular weight neural proteins (each with Mr less than 29,000) were identified as substrates for protein kinase C.
...
PMID:Reduced Na+ + K+-ATPase activity in peripheral nerve of streptozotocin-diabetic rats: a role for protein kinase C? 284 Mar 14

Single-stranded DNA-binding protein (SSB-protein) has been purified and characterized from Ehrlich ascite tumour (EAT) cells. The purification procedure was performed in analytical and preparative variants. It was shown that in the analytical variant of the purification procedure can be used to determine protein concentration in the cell. The molecular mass of the SSB-protein as determined by SDS polyacrylamide gel electrophoresis is 36 and 43 kD; that determined by gel filtration is 27, 28, 43 and 44 kD; pI is 7.4. The use of nitrocellulose filters showed that the SSB-protein binds preferentially to ss-DNA. The protein contains no admixtures of DNA-polymerases, endo- or exonucleases, DNA-dependent ATPase, lactate dehydrogenase and HMG-proteins. The SSB-protein stimulates 1.5-2-fold the activity of DNA-polymerase alpha from EAT, it does not activate DNA-polymerase beta from EAT and strongly inhibits the activity of exonuclease (snake venom phosphodiesterase). The specificity of the term "SSB-protein" which makes it different from other non-histone proteins of chromatin is discussed.
...
PMID:[Isolation and characteristics of single-stranded DNA-binding protein (SSB-protein) from Ehrlich ascites carcinoma cells]. 284 79

The surface activity and effect of histone, sodium deoxycholate and Triton X-100 on N+,K+-ATPase have been compared. It has been found that the coefficient of surface tightness on the borderline of suspension of ATPase containing membranes/air decreases with the increase in concentrations of these agents. The enzyme activity undergoes biphasic modification increasing with lower and decreasing with higher concentrations of the agents. The effectiveness of the agents depends on the charge of their molecules. The mechanism of interaction between Na+,K+-ATPase and the above modifiers is discussed.
...
PMID:[Dependence of Na, K-ATPase enzyme activity on the surface properties and charge of the substances interacting with the cell membrane]. 301 May 18


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

---