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)

The effects of the alpha-adrenergic agonist phenylephrine on the levels of adenosine 3':5'-monophosphate (cAMP) and the activity of the cAMP-dependent protein kinase in isolated rat liver parenchymal cells were studied. Cyclic AMP was very slightly (5 to 13%) increased in cells incubated with phenylephrine at a concentration (10(-5) M) which was maximally effective on glycogenolysis and gluconeogenesis. However, the increase was significant only at 5 min. Cyclic AMP levels with 10(-5) M phenylephrine measured at this time were reduced by the beta-adrenergic antagonist propranolol, but were unaffected by the alpha-blocker phenoxybenzamine, indicating that the elevation was due to weak beta activity of the agonist. When doses of glucagon, epinephrine, and phenylephrine which produced the same stimulation of glycogenolysis or gluconeogenesis were added to the same batches of cells, there were marked rises in cAMP with glucagon, minimal increases with epinephrine, and little or no changes with phenylephrine, indicating that the two catecholamine stimulated these processes largely by mechanisms not involving cAMP accumulation. DEAE-cellulose chromatography of homogenates of liver cells revealed two major peaks of cAMP-dependent protein kinase activity. These eluted at similar salt concentrations as the type I and II isozymes from rat heart. Optimal conditions for preservation of hormone effects on the activity of the enzyme in the cells were determined. High concentrations of phenylephrine (10(-5) M and 10(-4) M) produced a small increase (10 tp 16%) in the activity ratio (-cAMP/+cAMP) of the enzyme. This was abolished by propranolol, but not by phenoxybenzamine, indicating that it was due to weak beta activity of the agonist. The increase in the activity ratio of the kinase with 10(-5) M phenylephrine was much smaller than that produced by a glycogenolytically equivalent dose of glucagon. The changes in protein kinase induced by phenylephrine and the blockers and by glucagon were thus consistent with those in cAMP. Theophylline and 1-methyl-3-isobutylxanthine, which inhibit cAMP phosphodiesterase, potentiated the effects of phenylephrine on glycogenolysis and gluconeogenesis. The potentiations were blocked by phenoxybenzamine, but not by propranolol. Methylisobutylxanthine increased the levels of cAMP and enhanced the activation of protein kinase in cells incubated with phenylephrine. These effects were diminished or abolished by propanolol, but were unaffected by phenoxybenzamine. It is concluded from these data that alpha-adrenergic activation of glycogenolysis and gluconeogenesis in isolated rat liver parenchymal cells occurs by mechanisms not involving an increase in total cellular cAMP or activation of the cAMP-dependent protein kinase. The results also show that phosphodiesterase inhibitors potentiate alpha-adrenergic actions in hepatocytes mainly by a mechanism(s) not involving a rise in cAMP.
J Biol Chem 1976 Sep 10
PMID:Studies on the alpha-andrenergic activation of hepatic glucose output. II. Investigation of the roles of adenosine 3':5'-monophosphate and adenosine 3':5'-monophosphate-dependent protein kinase in the actions of phenylephrine in isolated hepatocytes. 0 57

A density gradient-purified microsomal membrane preparation from rabbit fundic gastric mucosa was used for a detailed study of the K+-stimulated ATPase and associated intermediate reactions. Membranes incubated with gamma-[32P]ATP show the rapid incorporation of 32P into phosphoprotein. Phosphoprotein levels were markedly reduced (1) when ATP hydrolysis went to completion or (2) upon addition of unlabeled ATP, thus suggesting the participation of a rapid turnover phosphorylated intermediate in the gastric microsomal ATPase. Addition of K+, Rb+ or Tl+ greatly reduced the level of the intermediate while stimulating ATPase activity; the observed affinities of these cations were similar for the effects on both ATPase and intermediate levels, with Tl+ greater than K+ greater than Rb+. Neither ATPase nor intermediate were stimulated by Na+, and ouabain was without effect on the reactions, thus differentiating this system from the (Na+ + K+)-ATPase. Addition of various inhibitors showed differential effects on the partial reactions of the gastric ATPase system. N-ethylmaleimide and Zn2+ showed characteristics of completely abolishing the K+-stimulated component of ATPase as well as the effects of K+ in reducing the level of intermediate, thus suggesting that these agents exert their inhibitory effect on a phosphoprotein phosphatase partial reaction. F- abolished the K+-stimulated ATPase, but its more complex effects on the intermediate suggested an additional reaction step within the domain of the phosphorylated intermediate. Results are consistent with a model system for the gastric microsomal ATPase involving a Mg2+-dependent protein kinase, a phosphorylated intermediate(s), and a K+-stimulated phosphoprotein phosphatase.
Biochim Biophys Acta 1976 Sep 07
PMID:Studies on the phosphorylated intermediates of a K+-stimulated ATPase from rabbit gastric mucosa. 0 43

Adenylate, guanylate cyclase and protein kinases in a fibrous sarcoma originating from rat prostate have been studied. A decrease in levels of adenosine 3', 5'-monophosphate (cyclic AMP) and adenylate cyclase activities and an increase in levels of guanosine 3',5'-monophosphate (cyclic GMP) and guanylate cyclase activities were observed in the tumor tissue when compared with the normal prostatic tissue of rats. Protein kinases from the tumor and the prostate were both responsive to exogenous cyclic AMP, with an apparent Ka of 0.08 muM in the tumor and of 0.11 muM in the prostate. It is of interest that the protein kinases from the tumor responded to cyclic AMP to the same extent as was observed in the enzyme preparation from the prostate. The protein kinase from the tumor was more sensitive to cyclic GMP than that from the prostate, showing an apparent Ka of 0.88 muM in the tumor and of 4.85 muM in the prostate. This tumor has been characterized with an increase in guanylate cyclase activities with a subsequent rise in cellular cyclic GMP and an increased sensitivity of the protein kinase to cyclic GMP.
Biochim Biophys Acta 1976 Sep 24
PMID:Studies on cyclic nucleotides in cancer. I. Adenylate guanylate cyclase and protein kinases in the prostatic sarcoma tissue. 0 48

Phosphorylation of the human erythrocyte membrane proteins by gamma (32P) ATP was studied at pH 6 and pH 7.4, at 30 degrees C, with incubation times varying from 5 to 90 minutes, and with or without cyclic AMP. Incorporated radioactivity was much higher at pH 7.4 because of the prevalent activity of cAMP independent protein-kinase. Maximum incorporation was obtained in both pH after 30-45 minutes incubation, thereafter incorporated radioactivity was either stable or decreased. The part of the radioactivity due to cAMP stimulation was low and seems constant with the incubation time. Analysis of the substrates showed the predominant cAMP independent protein kinase activity in the phosphorylation of the spectrin second component and component III and that of cAMP dependent activity in the phosphorylation of component II4, IV5 and other minor bands.
Pathol Biol (Paris) 1977 Sep
PMID:Phosphorylation of human erythrocyte membrane protein. Differences according to the assay procedure. 2 37

Cholesterol ester hydrolase activity was determined in preparations of rabbit and guinea pig aorta utilizing micellar and glycerol-dispersed cholesterol oleate substrates. Both substrate preparations demonstrated an acid pH optimum of 4--5 for the soluble and particulate rabbit media cholesterol ester hydrolase, suggesting a lysosomal origin for this activity. Approximately one-fifth of the total recovered activity was particulate. Particulate media preparations from guinea pig aorta also demonstrated cholesterol ester hydrolase activity at acid pH values with a definite optimum at pH 5 for the glycerol-dispersed substrate. However, in contrast to the rabbit media enzyme, activity was also observed at neutral pH with another optimum at pH 7. The supernatant enzyme from guinea pig media exhibited only a single pH optimum of 7. Cholesterol ester hydrolase activity from either rabbit or guinea pig media was not influenced by preincubation with cyclic AMP, ATP and protein kinase. The addition of chloroquine resulted in the inhibition of both the rabbit and guinea pig enzyme. Cholesterol ester hydrolase activity from rabbit and guinea pig media was also inhibited by phenyl methane sulfonyl fluoride; activity measured at pH 7 (guinea pig) was more sensitive to inhibition than activity measured at pH 5 (guinea pig and rabbit).
Atherosclerosis 1978 Sep
PMID:Characterization of cholesterol ester hydrolase activities in rabbit and guinea pig aortas. 3 Apr 61

Kinase activity detected in immune complexes containing the src gene product of the avian sarcoma virus has been reported. To further characterize this immune complex kinase, we developed a routine quantitative assay involving trichloroacetic acid precipitation on filters. The enzyme reaction required either Mg2+ or Mn2+, but was inactive with Ca2+. The kinetics of the phosphorylation reaction indicated a transient enzyme activity limited by rapid substrate-dependent inactivation of the enzyme. A variety of nucleoside and deoxyribonucleoside triphosphates (dATP, ATP, GTP, CTP, dGTP, TTP, dCTP) served as phosphoryl donors. The phosphorylation of immunoglobulin G was inhibited by the presence of nucleoside diphosphates. Deoxyribonucleoside diphosphates can either stimulate or inhibit the kinase reaction depending upon the concentration used. The unusual enzymatic properties of the immune complex kinase raise the possibility that the enzyme does not function as a protein kinase in vivo, but rather belongs to a different class of kinases (nucleotide kinases) which adventitiously phosphorylates immunoglobulin G when immunoprecipitated with immune serum.
J Virol 1979 Sep
PMID:Characterization of an immune complex kinase in immunoprecipitates of avian sarcoma virus-transformed fibroblasts. 4 53

Activity of RNA-dependent DNA polymerase (RDDP) from avian myeloblastosis virus (AMV), either in purified form or in virus lysates, was increased by phosphorylation. Stability of RDDP in lysates buffered with phosphate was much greater (no loss of activity in 48 hours at 4 degrees) than that in lysates buffered with Tris-Cl (76% loss). Activity lost in the Tris-buffered extracts was completely restored by phosphorylation. The findings suggested that AMV RDDP activity is influenced by the degree of phosphorylation of the enzyme or enzyme-associated proteins and that this chemical modification is mediated by protein phosphokinase and phosphoprotein phosphatase present in crude extracts of purified AMV. Application of these results provided the basis of procedures whereby RDDP can be recovered in significantly higher yield and purity than formerly.
Nucleic Acids Res 1976 Sep
PMID:Influence of phosphate on activity and stability of reverse transcriptase from avian myeloblastosis virus. 6 81

A cAMP-dependent protein kinase has been isolated from rabbit muscle and purified. The affinity constant of the enzyme for the nucleotide is Ka = 9.3 X 10(-9) M, with a Vmax = 0.013 X 10(12) moles bound cAMP/1 microgram protein. The influence exerted by different factors is studied: a) Inhibitor (I) of kinase activity: increases the binding capacity for cAMP, by percentages which depend on the amount of I. In the presence of inhibitor (120 microgram/100 microliter) the affinity constant is Ka = 4.1 X 10(-9) M, without change in Vmax. b) Effect of pH: it has a complex influence over binding, being also regulated by cAMP concentration. The positive effect on binding of ionic and bovine serum albumin concentrations, and the negative effect of enzyme preincubation before additions of (H3) cAMP, have also been studied. The importance of these effectors to obtain a high degree of sensitivity in the binding protein method has been assertained.
Rev Esp Fisiol 1978 Sep
PMID:Binding activity regulation of rabbit skeletal muscle adenosine 3'-5'-monophosphate-dependent protein kinases. 8 84

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.
J Biol Chem 1975 Sep 10
PMID:Reversibility of adenosine 3':5'-monophosphate-dependent protein kinase reactions. 16 60

Guanosine 3':5'-monophosphate(cyclic GMP)-dependent protein kinase which catalyzes the phosphorylation of histone was purified about 200-fold from the soluble fraction of pig lung by pH 5.5 precipitation, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration. The apparent Ka values for guanosine 3':5'-monophosphate and adenosine 3':5'-monophosphate were determined to be about 17 and 360 nM, respectively. Mg2+ was essential for the activity exhibiting biphasic stimulation behavior and neither Mn2+ nor Ca2+ could substitute for Mg2+. However, these divalent ions markedly inhibited the protein kinase activity stimulated by cyclic GMP in the presence of Mg2+.
J Biol Chem 1975 Sep 25
PMID:Partial purification and properties of guanosine 3':5'-monophosphate-dependent protein kinase from pig lung. 17 Feb 61


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