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1.
The lipid requirement of the (Ca2+ + Mg2+)-stimulated ATPase of human erythrocytes has been studied. The enzyme activity was lost after removal of the phospholipids using phospholipase A2 from Naja naja and serum albumin. Optimal restoration of the (Ca2+ + Mg2+)-ATPase activity in the partially lipid-depleted membranes was obtained with oleate. The reactivation was not due to the removal of a permeability barrier for ATP, since lysolecithin or cholate did not show latent activity. Reactivation was also obtained with several negatively charged phospholipids. Among the ones normally found in the erythrocyte membranes, only phosphatidyl serine reactivated significantly. 相似文献
2.
Doris Taylor Richard Baker Paul Hochstein 《Biochemical and biophysical research communications》1977,76(2):205-211
Incubation of red cells at 37° with the ionophore A23187 results in a loss of ATP that is dependent on the concentrations of A23187 and Ca2+ in the medium. ATP hydrolysis is greatest at micromolar concentrations of Ca2+ and decreases as Ca2+ in the medium is raised to millimolar levels. The ATP depletion is due to stimulation of calcium ATPase by A23187-mediated Ca2+ influx into the cell. The biphasic nature of Ca2+-stimulated ATP depletion in whole cells reflects the activity of Ca2+-ATPase in membrane preparations at varying Ca2+ concentrations. The ionophore can be removed by washing the cells with plasma or bovine serum albumin-containing medium and the ATP levels restored to normal by reincubating with 5 mM adenosine for 1 hr. 相似文献
3.
The spinach (Spinacia oleracea L.) leaf plasma membrane Ca2+-ATPase is regulated by calmodulin (3-fold stimulation) and limited proteolysis (trypsin; 4-fold stimulation). The plasma membrane Ca2+-ATPase was identified as a 120-kDa polypeptide on western immunoblots using two different antibodies. During trypsin treatment the 120-kDa band diminished and a new band appeared at 109 kDa. The appearance of the 109-kDa band correlated with the increase in enzyme activity following trypsin treatment. The stimulations by calmodulin and trypsin were not additive, suggesting that the 109-kDa polypeptide represents a Ca2+-ATPase lackin a terminal fragment involved in calmodulin regulation. This was confirmed by 125I-calmodulin overlay studies where calmodulin labeled the 120-kDa band in the presence of Ca2+, while the 109-kDa band did not bind calmodulin. The effects of calmodulin and limited proteolysis on ATP-dependent accumulation of 45Ca2+ in isolated inside-out plasma membrane vesicles were studied, and kinetical analyses performed with respect to Ca2+ and ATP. Calmodulin increased the Vmax. for Ca2+ pumping 3-fold, and reduced Km for Ca2+ from 1.6 to 0.9 µM. The Km for ATP (11 µM) was not affected by calmodulin. The effects of limited proteolysis on the affinities for Ca2+ and ATP were similar to those obtained with calmodulin. Notably, however, limited proteolysis increased the Vmax. for Ca2+ pumping to a higher extent than calmodulin, indicating incomplete calmodulin activation, or removal of an additional inhibitory site by trypsin. 相似文献
4.
《生物化学与生物物理学报:生物膜》1986,858(1):21-30
(1) Depending on the assay conditions, the ability of the Ca2+-ATPase from intact human red cell membranes to catalyze the hydrolysis of p-nitrophenylphosphate is elicited by either calmodulin or ATP. The response of the phosphatase activity to p-nitrophenylphosphate, ATP, Mg2+ and K+ is the same for the activities elicited by ATP or by calmodulin, suggesting that a single process is responsible for both activities. (2) In media with calmodulin, high-affinity activation is followed by high-affinity inhibition of the phosphatase by Ca2+ so that the activity becomes negligible above 30 μM Ca2+. Under these conditions, addition of ATP leads to a large decrease in the apparent affinity for inhibition by Ca2+. (3) In membranes submitted to partial proteolysis with trypsin, neither calmodulin nor Ca2+ are needed and phosphatase activity is maximal in media without Ca2+. This is the first report of an activity sustained by the Ca2+-ATPase of red cell membranes in the absence of Ca2+. Under these conditions, however, ATP still protects against high-affinity inhibition by Ca2+. These results strongly suggest that during activation by calmodulin, Ca2+ is needed only to form the calmodulin-Ca2+ complex which is the effective cofactor. (4) Protection by ATP of the inhibitory effects of Ca2+ and the induction of phosphatase activity by ATP + Ca2+ suggests that activation of the phosphatase by Ca2+ in media with ATP requires the combination of the cation at sites in the ATPase. (5) Results can be rationalized assuming that E2, the conformer of the Ca2+-ATPase, is endowed with phosphatase activity. Under this assumption, either the calmodulin-Ca2+ complex or partial proteolysis would elicit phosphatase activity by displacing the equilibrium between E1 and E2 towards E2. On the other hand, ATP + Ca2+ would elicit the activity by establishing through a phosphorylation-dephosphorylation cycle a steady-state in which E2 predominates over other conformers of the ATPase. 相似文献
5.
Electrical stimulation of the rat heart sarcolemmal membranes with a square wave current was found to increase Ca2+-ATPase activity. This activation of the enzyme was dependent upon the voltage of the electric current, frequency of stimulation and duration of stimulation of the sarcolemmal membranes. The increase in ca2+-ATPase was reversible upon terminating the electrical stimulation. The activation of sarcolemmal Ca2+-ATPase due to electrical stimulation was markedly depressed when the reaction was carried out at high pH (7.8 to 8.2), low pH (6.6 to 7.0), high temperatures (45 to 50°C) and low temperatures (17 to 25°C) of the incubation medium. Ca2+-antagonists, verapamil and D-600, unlike other types of inhibitors such as propranolol and ouabain, were found to reduce the activation of sarcolemmal Ca2+-ATPase by electrical stimulation. These results support the view that Ca2+/Mg2+ ATPase may be involved in the gating mechanism for opening Ca2+-channels in the sarcolemmal membrane upon excitation of the cardiac muscle. 相似文献
6.
Human red cells (RBC) were loaded with moderate amounts of Ca2+ by the ionophore A23187. Quantitative relationships between Ca2+-loading, ATP consumption and glycolytic flux were established. 1. Ca2+-loading is accompanied by ATP depletion. A maximum ATP consumption of approximately 10 mmoles/l RBC/h was estimated. 2. There is a positive correlation between lactate formation and Ca2+-loading. This is linear from 1.4 to about 4 mmoles lactate/l RBC/h. 3. Ca2+-induced glycolytic stimulation seems not to be mediated by adenine nucleotides. A wide range of energy charges and very different adenine nucleotide patterns were associated with the same stimulation of lactate production. 4. The turnover of the (Ca2+-Mg2+)-ATPase and its share in the Ca2+-stimulated ATP consuming processes were estimated with inhibitors. 1 mM La3+ inhibited both Ca2+-outward transport and ATP consumption by 80%. The remaining 20% of the ATP consumption was accounted for by the (Na+-K+)-ATPase. 5. A Ca2+ extrusion to ATP consumption molar ratio of 2:1 was found. However, when ATP consumption was due to the breakdown of previously accumulated glycolytic intermediates, the ratio dropped to about 1. 相似文献
7.
Human red cells (RBC) were loaded with moderate amounts of Ca2+ by the ionophore A23187. Quantitative relationships between Ca2+-loading, ATP consumption and glycolytic flux were established. 1. Ca2+-loading is accompanied by ATP depletion. A maximum ATP consumption of approximately 10 mmoles/l RBC/h was estimated. 2. There is a positive correlation between lactate formation and Ca2+-loading. This is linear from 1.4 to about 4 mmoles lactate/l RBC/h. 3. Ca2+-induced glycolytic stimulation seems not to be mediated by adenine nucleotides. A wide range of energy charges and very different adenine nucleotide patterns were associated with the same stimulation of lactate production. 4. The turnover of the (Ca2+-Mg2+)-ATPase and its share in the Ca2+-stimulated ATP consuming processes were estimated with inhibitors. 1 mM La3+ inhibited both Ca2+-outward transport and ATP consumption by 80%. The remaining 20% of the ATP consumption was accounted for by the (Na+-K+)-ATPase. 5. A Ca2+ extrusion to ATP consumption molar ratio of 2:1 was found. However, when ATP consumption was due to the breakdown of previously accumulated glycolytic intermediates, the ratio dropped to about 1. 相似文献
8.
Summary Human erythrocyte Ca2+-translocating ATPase was solubilized from calmodulin-depleted membranes using the detergent Triton X-100, and subsequently purified by calmodulin-affinity chromatography. The purified enzyme was reconstituted in artificial phospholipid vesicles using a cholate-dialysis method and various phospholipids. The reconstituted enzyme was able to translocate Ca2+ inside the vesicles, both in the absence and in the presence of the Ca2+-chelating agent, oxalate, inside the vesicles. The tightness of coupling between ATP hydrolysis and cation translocation was investigated by the use of different ionophoretic compounds. The efficiency of Ca2+ translocation was measured by the ability of the ionophores to stimulate ATP hydrolytic activity of the reconstituted enzyme. It was found that the maximum stimulation of the ATP hydrolytic activity was induced by the electroneutral Ca2+/2H+ ionophore A23187 (9 to 10-fold). A Ca2+ ionophore unable to translocate H+, CYCLEX-2E, was less efficient in stimulating the activity of the reconstituted enzyme (two- to threefold). However, the combined addition of CYCLEX-2E plus protonophores further increased the ATP hydrolytic activity (around fourfold), whereas, the protonophores did not further stimulate ATP hydrolysis in the presence of A23187. Furthermore, in the absence of Ca2+ ionophore, the electroneutral K+(Na+)/H+ ionophoretic exchanger, nigericin, or the electroneutral Na+(K+)/H+ ionophoretic exchanger, monensin, stimulated the rate of ATP hydrolysis in the reconstituted enzyme two- or threefold, respectively. These results suggest that the Ca2+-ATPase not only translocates Ca2+ but also H+ in the opposite direction. 相似文献
9.
J. P. Infante 《Molecular and cellular biochemistry》1987,74(2):111-116
A critical review of the experimental literature concerning the metabolism of all-cis-4, 7, 10, 13, 16, 19-docosahexaenoate-containing phospholipids in muscle and retina suggests that it plays an essential role in maximizing the Ca2+/ATP stoichiometry of the Ca2+-ATPase of sarcoplasmic reticulum and retinal photoreceptor disks. Docosahexaenoate-phosphatidylcholine is proposed to participate in oligomerization of Ca2+-ATPase necessary for the establishment of a high Ca2+/ATP coupling ratio of the Ca2+ pump in these tissues. Possible tests of this hypothesis are presented. 相似文献
10.
Kabeer I. Ahammad Sahib Durisala Desaiah 《Journal of biochemical and molecular toxicology》1986,1(4):55-66
Previous studies from this laboratory have indicated that tricyclohexyltin hydroxide (Plictran) is a potent inhibitor of both basal- and isoproterenol-stimulated cardiac sarcoplasmic reticulum (SR) Ca2+-ATPase, with an estimated IC-50 of 2.5 × 10?8M. The present studies were initiated to evaluate the mechanism of inhibition of Ca2+-ATPase by Plictran. Data on substrate and cationic activation kinetics of Ca2+-ATPase indicated alteration of Vmax and Km by Plictran (1 and 5×10?8M), suggesting a mixed type of inhibition. The beta-adrenergic agonist isoproterenol increased Vmax of both ATP- and Ca2+-dependent enzyme activities. However, the Km of enzyme was decreased only for Ca2+ Plictran inhibited isoproterenol-stimulated Ca2+-ATPase activity by altering both and Vmax and Km of ATP as well as Ca2+-dependent enzyme activities, suggesting that after binding to a single independent site, Plictran inhibits enzyme catalysis by decreasing the affinity of enzyme for ATP as well as for Ca2+ Preincubation of enzyme with 15 μM cAMP or the addition of 2mM ATP to the reaction mixture resulted in slight activation of Plictran-inhibited enzyme. Pretreatment of SR with 5 × 10?7M propranolol and 5 × 10?8M Plictran resulted in inhibition of basal activity in addition to the loss of stimulated activity. Preincubation of heart SR preparation with 5 × 10?5M coenzyme A in combination with 5 × 10?8M Plictran partly restored the beta-adrenergic stimulation. These results suggest that some critical sites common to both basal- and beta-adrenergic-stimulated Ca2+-ATPase are sensitive to binding by Plictran, and the resultant conformational change may lead to inhibition of beta-adrenergic stimulation. 相似文献
11.
Inhibition of calcium transport in sarcoplasmic reticulum after modification of highly reactive amino groups 总被引:1,自引:0,他引:1
C Hidalgo 《Biochemical and biophysical research communications》1980,92(3):757-765
Partial labeling of the amino groups of sarcoplasmic reticulum with a complex of fluorescamine with cycloheptaamylose in the presence of ATP results in marked inhibition of Ca2+ transport without affecting the enzyme phosphorylation or the Ca2+-ATPase activity. Fast labeling, which parallels the time course of inhibition of Ca2+ transport, takes place into phosphatidylethanolamine; a slower labeling of the Ca2+-ATPase polypeptide was observed. Vesicles in which mainly phosphatidylethanolamine has reacted with the label retain their impermeability barrier to Ca2+, as judged by Ca2+ efflux measurements and by the stimulation of Ca2+-ATPase activity produced by the ionophore A23187. These results suggest that modification of fast-reacting amino groups interferes specifically with the calcium translocation reaction. 相似文献
12.
The sickle cell (Hb SS) membrane-bound Ca2+-ATPase was found to have a Vmax in the range of 30–100% of the Vmax of the normal enzyme. In all sickle cell preparations, the Ca2+-ATPase could be stimulated at least 4-fold by calmodulin, but the stimulation factor varied considerably (4–26 fold) in the different preparations. The affinity of the ghost sickle cell Ca2+-ATPase for Ca2+, ATP and calmodulin was comparable to that of the normal enzyme. The sickle cell Ca2+-ATPase was solubilized from the membrane with Triton-X-100, and purified through a calmodulin sepharose-4B column, a technique by which the Ca2+-ATPase from normal ghosts has been successfully isolated in a functionally active and pure form (see V. Niggli, E.S. Adynyah, J.T. Penniston and E. Carafoli, 1981, J.Biol.Chem.256,. 395 – 401). The specific activity of the isolated sickle cell enzyme was significantly decreased (up to 80%) with respect to that of the normal enzyme, but the amount of protein isolated was comparable to normal. All other parameters of the ATPase (affinity for Ca2+, ATP and calmodulin) were comparable to those found for the normal enzyme. In SDS polyacrylamide gel electrophoresis, the purified enzyme appeared as a single band protein with a Mr comparable to that of the normal enzyme. In the absence of calmodulin the sickle cell enzyme could be activated by acidic phospholipids, as reported for the normal enzyme. After reconstitution into liposomes it transported Ca2+ with normal efficiency (about 1 hydrolyzed). Therefore, the only difference between the purified normal and the sickle cell enzyme appears to be the lower specific activity of the latter. 相似文献
13.
Sidney Katz Basil D. Roufogalis Amiram D. Landman Larry Ho 《Journal of cellular biochemistry》1979,10(2):215-225
Erythrocyte membranes prepared by three different procedures showed (Mg2+ + Ca2+)-ATPase activities differing in specific activity and in affinity for Ca2+. The (Mg2+ + Ca2+)-ATPase activity of the three preparations was stimulated to different extents by a Ca2+-dependent protein activator isolated from hemolystes. The Ca2+ affinity of the two most active preparations was decreased as the ATP concentration in the assay medium was increased. Lowering the ATP concentration from 2 mM to 2–200 μM or lowering the Mg:ATP ratio to less than one shifted the (Mg2+ + Ca2+)-ATPase activity in stepwise hemolysis membranes from mixed “high” and “low” affinity to a single high Ca2+ affinity. Membranes from which soluble proteins were extracted by EDTA (0.1 mM) in low ionic strengh, or membranes prepared by the EDTA (1–10 mM) procedure, did not undergo the shift in the Ca2+ affinity with changes in ATP and MgCl2 concentrations. The EDTA-wash membranes were only weakly activated by the protein activator. It is suggested that the differences in properties of the (Mg2+ + Ca2+)-ATPase prepared by these three procedures reflect differences determined in part by the degree of association of the membrane with a soluble protein activator and changes in the state of the enzyme to a less activatable form. 相似文献
14.
In both cardiac and slow-twitch skeletal muscle sarcoplasmic reticulum (SR) there are several systems involved in the regulation of Ca2+-ATPase function. These include substrate level regulation, covalent modification via phosphorylation-dephosphorylation of phospholamban by both cAMP-dependent protein kinase (PKA) and Ca2+/calmodulin-dependent protein kinase (CaM kinase) as well as direct CaM kinase phosphorylation of the Ca2+-ATPase. Studies comparing, the effects of PKA and CaM kinase on cardiac Ca2+-ATPase function have yielded differing results; similar studies have not been performed in slow-twitch skeletal muscle. It has been suggested recently, however, that phospholamban is not tightly coupled to the Ca2+-ATPase in SR vesicles from slow-twitch skeletal muscle. Our results indicate that assay conditions strongly influence the extent of CaM kinase-dependent Ca2+-ATPase stimulation seen in both cardiac and slow-twitch skeletal muscle. Addition of calmodulin (0.2 M) directly to the Ca2+ transport assay medium results in minimal ( 112–130% of control) stimulation of Ca2+ uptake activity when the Ca2+ uptake reaction is initiated by the addition of either ATP or Ca2+/EGTA. On the other hand, prephosphorylation of the SR by the endogenous CaM kinase and subsequent transfer of the membranes to the Ca2+ transport assay medium results in stimulation of Ca2+ uptake activity (202% of control). These effects are observable in both cardiac and slow-twitch skeletal muscle SR. PKA stimulates Ca2+ uptake markedly (215% of control) when the Ca2+ uptake reaction is initiated by the addition of prephosphorylated SR membranes or by Ca2+/EGTA but minimally (130% of control) when the Ca2+ uptake reaction is initiated by the addition of ATP. These findings imply that (a) phospholamban is coupled to the Ca2+-ATPase in slow-twitch skeletal muscle SR (as in cardiac SR), and (b) the amount of Ca2+ uptake stimulation seen upon the addition of calmodulin or PKA depends strongly on the assay conditions employed. Our observations help to explain the wide range of effects of calmodulin or PKA addition reported in previous studies. It should be noted that, since CaM kinase is now known to phosphorylate the Ca2+-ATPase in addition to phospholamban, further studies are required to determine the relative contributions of phospholambanversus Ca2+-ATPase phosphorylation in the stimulation of Ca2+-ATPase function by CaM kinase. Also, earlier studies attributing all of the effects of CaM kinase stimulation of Ca2+ uptake and Ca2+-ATPase activity to phospholamban phosphorylation need to be re-examined. 相似文献
15.
亲和层析纯化肌质网Ca2+-ATP酶 总被引:1,自引:1,他引:0
建立了一种亲和层析纯化肌质网Ca2+-ATP酶的方法.用非离子型去污剂C12E8 溶解肌质网,再通过反应红-120琼脂糖亲和层析柱使肌质网Ca2+-ATP酶纯度从粗品中的65%提高到99%,并具有较高ATP水解活性.经SDS-聚丙烯酰胺凝胶电泳检测,为电泳纯. 相似文献
16.
Kevin K. W. Wang Basil D. Roufogalis Antonio Villalobo 《The Journal of membrane biology》1989,112(3):233-245
Summary Calpain I purified from human erythrocyte cytosol activates both the ATP hydrolytic activity and the ATP-dependent Ca2+ transport function of the Ca2+-translocating ATPase solubilized and purified from the plasma membrane of human erythrocytes and reconstituted into phosphatidylcholine vesicles. Following partial proteolysis of the enzyme by calpain I, both the initial rates of calcium ion uptake and ATP hydrolysis were increased to near maximal levels similar to those obtained upon addition of calmodulin. The proteolytic activation resulted in the loss of further stimulation of the rates of Ca2+ translocation or ATP hydrolysis by calmodulin as well as an increase of the affinity of the enzyme for calcium ion. However, the mechanistic Ca2+/ATP stoichiometric ratio was not affected by the proteolytic treatment of the reconstituted Ca2+-translocating ATPase. The proteolytic activation of the ATP hydrolytic activity of the reconstituted enzyme could be largely prevented by calmodulin. Different patterns of proteolysis were obtained in the absence or in the presence of calmodulin during calpain treatment: the 136-kDa enzyme was transformed mainly into a 124-kDa active ATPase fragment in the absence of calmodulin, whereas a 127-kDa active ATPase fragment was formed in the presence of calmodulin. This study shows that calpain I irreversibly activates the Ca2+ translocation function of the Ca2+-ATPase in reconstituted proteoliposomes by producing a calmodulin-independent active enzyme fragment, while calmodulin antagonizes this activating effect by protecting the calmodulin-binding domain against proteolytic cleavage by calpain. 相似文献
17.
1. In the presence of ATP, the Ca2+ pump of human red cell membranes catalyzes the hydrolysis of phosphate. The requirement for ATP of the Ca2+- activity was studied in relation to the two classes of site for ATP that are apparent during Ca2+ -ATPase activity. 2. (a) The for ATP as activator of the Ca2+ - extrapolated at 0 mM PNPP is equal to the of the Ca2+ -ATPase. (b) PNPP competes with ATP and its effectiveness is the same regardless the nucleotide acts as the substrate of the Ca2+ -ATPase or as activator of the Ca2+ -. 3. PNPP at the high-affinity site does not substitute for ATP as activator of the Ca2+ -. 4. At ATP concentrations that almost saturate the high-affinity site, Ca2+ - activity increases as a function of PNPP along an S-shaped curve, while Ca2+ -ATPase activity is partially inhibited along a curve of the same shape and apparent affinity. The fraction of Ca2+ -ATPase activity which is inhibited by PNPP is that which results from occupation of the low-affinity site by ATP. 5. Activation of the Ca2+ -ATPase by ATP at the low-affinity site is associated with inhibition of the Ca2+ - activity. Both phenomena take place with the same apparent affinity and along curves of the same shape. 6. Experimental results suggest that: (a) the Ca2+ - activity depends on ATP at the high-affinity site; (b) PNPP is hydrolyzed at the low-affinity site; (c) Ca2+ -ATPase activity at the high-affinity size persists during Ca2+ - activity. 相似文献
18.
Chemical cross-linking was used to study protein binding interactions between native phospholamban (PLB) and SERCA2a in sarcoplasmic reticulum (SR) vesicles prepared from normal and failed human hearts. Lys27 of PLB was cross-linked to the Ca2+ pump at the cytoplasmic extension of M4 (at or near Lys328) with the homobifunctional cross-linker, disuccinimidyl glutarate (7.7 Å). Cross-linking was augmented by ATP but abolished by Ca2+ or thapsigargin, confirming in native SR vesicles that PLB binds preferentially to E2 (low Ca2+ affinity conformation of the Ca2+-ATPase) stabilized by ATP. To assess the functional effects of PLB binding on SERCA2a activity, the anti-PLB antibody, 2D12, was used to disrupt the physical interactions between PLB and SERCA2a in SR vesicles. We observed a tight correlation between 2D12-induced inhibition of PLB cross-linking to SERCA2a and 2D12 stimulation of Ca2+-ATPase activity and Ca2+ transport. The results suggest that the inhibitory effect of PLB on Ca2+-ATPase activity in SR vesicles results from mutually exclusive binding of PLB and Ca2+ to the Ca2+ pump, requiring PLB dissociation for catalytic activation. Importantly, the same result was obtained with SR vesicles prepared from normal and failed human hearts; therefore, we conclude that PLB binding interactions with the Ca2+ pump are largely unchanged in failing myocardium. 相似文献
19.
Danuta Kosk-Kosicka 《Molecular and cellular biochemistry》1990,99(2):75-81
We have compared properties of the red blood cell Ca2+-ATPase in two types of preparations: red cell membrane ghosts (enzyme in unfractionated membranes) and after purification (detergent-soluble enzyme). The Ca2+-ATPase activity was studied with respect to its requirement for: calmodulin, calcium, magnesium, monovalent cations, ionic strength, pH, and temperature. Sensitivity of the Ca2+-ATPase activity in the two preparations to anticalmodulin drugs and to engineered calmodulins with amino acid substitutions was determined. Finally, stoichiometry of the formation of phosphorylated enzyme intermediate (EP) and titrations of the ATP binding region with fluorescein 5-isothiocyanate (FITC) were characterized. For the first time a high phosphorylation level of 2.0–2.4 mmol EP/mg of purified enzyme is reported.The two enzyme preparations have been found to be very similar with respect to the dependency of all the regulating factors described here. These results complement findings reported from various laboratories on the similarity of other kinetic properties as well as the similarity of modulation of the Ca2+-ATPase activity by phospholipids and proteolysis in the membranous and purified enzyme. Thus, the purified detergent-soluble enzyme is very well suited for kinetic characterization of the red cell Ca2+-ATPase. 相似文献
20.
Chang E Hornick K Fritz KI Mishra OP Delivoria-Papadopoulos M 《Neurochemical research》2007,32(7):1142-1149
There is growing concern over detrimental neurologic effects to human newborns caused by increased inspired oxygen concentrations.
We hypothesize that hyperoxia (FiO2 > 0.95) results in increased high-affinity Ca2+-ATPase activity, Ca2+-influx, and proapoptotic protein expression in cortical neuronal nuclei of newborn piglets. Neuronal cerebral energy metabolism
was documented by determining ATP and phosphocreatine levels. Neuronal nuclear conjugated dienes and fluorescent compounds
were measured as indices of lipid peroxidation. High-affinity Ca2+-ATPase activity and ATP-dependent Ca2+-influx were determined to document neuronal nuclear membrane function. Hyperoxia resulted in increases in lipid peroxidation,
high-affinity Ca2+-ATPase activity, ATP-dependent Ca2+-influx, and Bax/Bcl-2 ratio in the cortical neuronal nuclei of newborn piglets. We conclude that hyperoxia results in modification
of neuronal nuclear membrane function leading to increased nuclear Ca2+-influx, and propose that hyperoxia-induced increases in intranuclear Ca2+ activates the Ca2+/calmodulin-dependent protein kinase pathway, triggering increased CREB protein-mediated apoptotic protein expression in hyperoxic
neurons. 相似文献