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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two rabbit erythrocyte casein kinases, GTP:casein kinase I and GTP:casein kinase II, have been purified 29 000- and 47 000-fold, respectively. Studies employing sucrose density gradient centrifugation indicate that kinase I has a molecular weight of about 9.5 - 10(5) (25 S) and kinase II about 1.4 - 10(6) (32 S). These enzymes can utilize either ATP or GTP as the phosphoryl donor. Among various protein substrates examined, these kinases catalyze the phosphorylation of casein greater than 50% dephosphorylated phosvitin congruent to 50% dephosphorylated casein greater than phosvitin. Histones, protamine and bovine serum albumin are poor phosphoryl acceptors. Kinetic data indicate that both enzymes are inhibited by high casein substrate concentrations which may be partially relieved by NaCl. Both phosphotransferases require Mg(2+) for activity and are optimally active at pH 9.0. The enzymes have apparent Km values of 2.5 - 10(-5) M for GTP, 2 - 10(-5) M for ATP, and 0.4--0.6 mg/ml for casein. The incorporation of the terminal phosphate of GTP into casein as catalyzed by these enzymes is inhibited to varying degrees by ATP, ITP, ADP, and GDP but not by UTP, CTP, GMP, adenosine 3':5'-cyclic monophosphate, and guanosine 3':5'-cyclic monophosphate. In addition, NaF and 2,3-diphosphoglyceric acid are also found to inhibit the activity of both kinases. The effect of 2,3-diphosphoglycerate is interesting and suggests that this metabolite may regulate the activity of the casein kinases in the red blood cells.
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PMID:Multiple forms of casein kinase from rabbit erythrocytes. 0 76

Two different mechanisms for the active accumulation of Ca2+ by subcellular fractions of human umbilical artery are described. One, located in the mitochondrial fraction, was induced by exogenous ATP or respiratory substrates (ADP and succinate) and was inhibited by azide. The other, located in the microsomal fraction, was induced by ATP and potentiated by oxalate, but not inhibited by azide. Increasing ATP concentrations up to 4-5 mM increased microsomal Ca2+ accumulation, whereas increasing ATP concentration above 2-3 mM caused inhibition of mitochondrial Ca2+ uptake. Although changing pH from 7.4 to 7.2 had no effect on mitochondrial Ca2+ accumulation, it doubled microsomal uptake. Neither adenosine 3',5'-monophosphate nor guanosine 3',5'-monophosphate in the presence or absence of protein kinase and kinase modulator affected Ca2+ uptake by or phosphorylation of the subcellular fractions. Partially purified protein kinases from umbilical and beef skeletal muscle contained a component(s) distinguishable from the kinase on the basis of its heat stability that enhanced ATP-induced Ca2+ uptake by mitochondrial fractions from the umbilical artery. It is suggested that alterations in Ca2+ sequestration induced by changes in ATP concentration and intracellular pH in mitochondrial and microsomal fractions, respectively, could play a role in the control of arterial patency and closure with changes in PO2.
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PMID:Calcium uptake by subcellular fractions of human umbilical artery. 1 Jul 37

An apparent enigma during platelet aggregation is that increased glycogenolysis occurs despite a fall in cyclic AMP levels; Activation by a classical cascade is therefore unlikely, and an alternative stimulus for phosphorylase a formation was sought. It was found that low levels of Ca-2+ markedly activate phosphorylase b kinase from human platelets, with a Ka of 0i muM Ca-2+, which is similar to that for the skeletal muscle enzyme; The kinase activity is unstable, and on enzyme ageing is a 50% loss in activity with the Ka decreasing to 0.33 muM Ca-2+. In unstilulated platelets, phosphorylase a was 13.3% of toal measured activity, and glycogen synthetase I was 32.3%. Aggregation induced by ADP did not change the percentage of I synthetase, while increasing that for phosphorylase a. Dibutyryl cyclic AMP did, as expected, increase the percentage of both phosphorylated enzymes; These findings suggest that the natural activator of platelet glycogenolysis during aggregation is Ca-2+, which directly stimulates phosphorylase b kinase without altering glycogen synthetase activity. The cyclic AMP-dependent protein kinase does not appear to be involved;
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PMID:Control of platelet glycogenolysis; Activation of phosphorylase kinase by calcium. 16 52

A protein phosphokinase (ATP: protein phosphotransferase EC 2.7.1.37) which is stimulated by 3',5'-cyclic adenosine monophosphate (cyclic AMP) has been partially purified from both the cytoplasmic and membrane fractions of human platelets. The kinetics of both enzymes preparations are similar in respect to cyclic AMP, ATP, ADP and AMP. 5-10-minus 7 M cyclic AMP stimulated both preparations by approximately 100%. Both ADP and AMP at a concentration of 5-10-minus 5 M inhibited protein phosphokinase activity of the soluble and membrane preparation by between 50% and 70%. The response of the two enzyme preparations to calcium differed. 10 mM Ca-2+ inhibited soluble protein phosphokinase activity approximately 80% both in the presence and absence of 5-10 minus 7 M cyclic AMP whereas the same concentrations of Ca-2+ inhibited the membrane-bound enzyme by approximately 60% in the presence of 5-10-minus 7 M cyclic AMP and 40% in the absence of cyclic AMP. This observation may be of importance in understanding the mechanism of platelet aggregation.
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PMID:The effect of ADP, calcium and some inhibitors of platelet aggregation on protein phosphokinases from human blood platelets. 16 30

Polyphosphate kinase, an enzyme which incorporated the gamma-phosphate of ATP into long-chain polyphosphate molecules, was purified more than 700-fold from Arthrobacter atrocyaneus by ammonium sulphate fractionation, DEAE-cellulose column chromatography and Ssphadex G-200 gel filtration. The enzyme had a broad pH optimum at 6-0 to 7-0 and required Mn2+ or Mg2+, histone, and inorganic phosphate for activity. The Km for Mn-ATP was 0-53 mM, and for inorganic phosphate was 1-67 mM. Free ATP concentrations greater than 8 muM inhibited the enzyme. Free Mn2+ or Mg2+ concentrations greater than 2 mM or 6 mM, respectively, were also inhibitory. Activity was strongly inhibited by 4 mM-ADP, 1 mM-PP1 or 20 mM-NaF. The effect of ADP might have resulted from reversing the equilibrium of the kinase reaction. The activation by phosphate ions might indicate a role for the enzyme in regulating intracellular phosphate levels or maintaining a phosphorus reserve. The level of enzymic activity in the bacteria responded to changes in inorganic phosphate concentration in the medium. Basic proteins, such as protamine, could substitute for histone as activator. Proteins such as casein or bovine serum albunim would also substitute for histone but only in the absence of inorganic phosphate. The presence of a protein might be necessary to form a complex with the product, thus preventing reversal of the reaction in vitro. The reaction product was characterized, and found to be labile in hydroxylamine, base, and acid at 100 degrees C. It behaved as a long-chain-polyphosphate molecule on chromatography in an Ebel's solvent. The enzymic activity was therefore not that of a protein kinase.
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PMID:Purification and characterization of a polyphosphate kinase from Arthrobacter atrocyaneus. 16 7

Using a homogeneous enzyme from rabbit skeletal muscle, it has been demonstrated that the cyclic adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase reaction is reversible. In addition to the phosphorylated protein substrate, the reverse reaction requires Mg2+, ADP, and cyclic AMP when the holoenzyme is used as the source of enzyme. It is independent of cyclic AMP when the catalytic subunit of the protein kinase is used. The optimum pH for the reverse reaction with 32P-labeled casein as the substrate is 5.7, essentially the same as that for the forward reaction. Among the nucleotide subtrates tested, ADP serves as the best phosphoryl group acceptor. The Km of the enzyme for ADP is 3.3 mM and that for 32P-casein is 1.7 mg/ml. The equilibrium constant at 30 degrees is approximately 0.042 at a magnesium concentration of 10 mM and a pH of 6.9. This result indicates that the free energy of hydrolysis (deltaG0obs) of the phosphorylated protein substrate is relatively high, i.e. approximately -6.5 kcal/mol under these conditions.
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PMID:Reversibility of adenosine 3':5'-monophosphate-dependent protein kinase reactions. 16 60

8-Azidoadenosine 3',5'-monophosphate (8-N3-cAMP) containing 32P has been used as a photoaffinity label specific for the adenosine 3',5'-monophosphate (cAMP) binding site(s) present in a partially purified preparation of soluble protein kinase from bovine brain. 8-N3-cAMP and cAMP were found to compete for the same binding site(s) in this preparation, as determined by a standard filter assay. When this protein preparation was equilibrated with [32P]-8-N3-cAMP, and then irradiated at 253.7 nm, the incorporation of radioactivity was predominantly into a protein with an apparent molecular weight of 49,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. This labeled protein comigrated in the gel with the only protein which is endogenously phosphorylated by [gamma-32P]ATP, a protein which has been shown to be the regulatory subunit of the protein kinase (H. Maeno, P. L. Reyes, T. Ueda, S. A. Rudolph, and P. Greengard (1974), Arch. Biochem. Biophys. 164, 551). The incorporation of [32P]-8-N3-cAMP into this protein was half-maximal at a concentration of 7 x 10(-8) M. In accordance with a proposed mechanism involving the formation of a highly reactive nitrene intermediate upon irradiation of the azide, the incorporation of radioactivity into protein was maximal within 10 min of irradiation, and was almost eliminated by preirradiation of the photolabile ligand. Moreover, this incorporation was virtually abolished by a 50-fold excess of cAMP, but not by AMP, ADP, ATP, or adenosine. We suggest that 8-N3-cAMP may prove to be a useful molecular probe of the cAMP-binding site in receptor proteins and report its use in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a highly sensitive and selective radiochemical marker for cAMP-binding proteins.
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PMID:Photoaffinity labeling of a protein kinase from bovine brain with 8-azidoadenosine 3',5'-monophosphate. 16 88

Testicular and cauda epididymal sperm were obtained via catheters previously implanted in the rete testis and proximal vas deferens of bulls and were used to examine the relationships among sperm motility, cyclic adenosine 3':5'-monophosphate (cAMP) level, adenine nucleotide levels, and rates of glucose and oxygen consumption. Testicular, cauda epididymal, and ejaculated sperm contain cAMP-stimulated protein kinase, adenylate cyclase, and nucleotide phosphodiesterase. Treatment of the nonmotile testicular sperm with phosphodiesterase inhibitors resulted in a doubling of cellular cAMP concentration and a 25% increase in their glucose consumption. No change in motility, ATP level, or rate of oxygen consumption was observed. Sperm in neat cauda epididymal semen had flagellating tails but no progressive motility. Dilution of these sperm into glucose-containing buffer resulted in an increase in intracellular cAMP concentration and a decrease in ATP level with concomitant increases in ADP and AMP levels. These biochemical changes occurred within 30 s after dilution and apparently preceded the initiation of progressive motility by most cells. Since sperm in neat cauda epididymal semen became progressively motile when diluted with neat cauda epididymal plasma as well as accessory sex gland fluid or buffer, composition of the fluid surrounding the sperm is not responsible for the initiation of progressive motility upon dilution nor does cauda epididymal plasma contain an inhibitory factor. Perhaps release from contact immobilization provides the stimulation for the initial acquisition of progressive motility by cauda epididymal sperm. We conclude that during epididymal passage sperm develop from a cell physically unresponsive to changes in cAMP concentration to a form which initiates progressive motility upon changes in cAMP concentration.
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PMID:Adenine nucleotide changes at initiation of bull sperm motility. 17 61

A nucleoside-dependent protein kinase (EC 2.7.1.37) was partially purified from Trypanosoma gambiense, the pathogenic agent of sleeping sickness. This enzyme catalyzes the phosphorylation of histone and protamine. Various nucleosides at the concentration of 10(-4) M stimulated the histone kinase activity about two-fold, whereas cyclic AMP and cyclic GMP were without effect. The pH-optimum for histone phosphorylation was at about pH 7.0. The enzyme activity absolutely depends on Mg2+, Mn2+ or Co2+. The apparent Km-value for histone was 0.3 mg/ml and those for ATP were 2 - 10(-4) M and 6 - 10(-5) M in the absence or presence of 10(-4) M adenosine respectively. IDP and ADP complete with ATP. The inhibition constants were calculated to be 2 - 10(-4) M and 2.5 - 10(-4) M, respectively. The molecular weight of the histone kinase was found to be 95 000 by gel filtration and 88 000 by sedimentation in a sucrose gradient.
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PMID:Nucleoside-dependent protein kinase from Trypanosoma gambiense. 17 63

Disulfide reductase (DSR) of mice liver supernatant is kinetically demonstrated as associating-dissociating oligomeric protein with positive homotropic cooperativity for the substrate. Cyclic 3',5'-AMP (10(-11)--10(-5) M) activates DSR and increases V, but does not change either [S]0,5, nor nH and does not shift the plot of specific activity versus the enzyme concentration. ATP, GTP, UTP, CTP, protamine, histone, Mg2+, Ca2+, EDTA (but not adenosine, 5'-AMP, 2'3'-AMP, ADP beef serum albumin) activated DSR. The effects of different modifiers are not summed up. Preincubation is essential for the action of the majority of the activators. Heating for 8 minutes at 55 degrees C desensitized completely DSR to all the modifiers without changing its catalytic activity, [S]0,5 and nH values. Possible mechanisms of activation of DSR, especially the involvement of protein kinase, are discussed.
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PMID:[Kinetics and regulatory properties of the disulfide reductase enzyme from mouse liver]. 17 10


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