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 protein kinase associated with virions of frog virus 3 was purified to apparent homogeneity by ion exchange chromatography and gel filtration. The enzyme protein appeared as a single polypeptide of molecular weight 50,000 to 55,000 as determined by gel filtration, glycerol gradient sedimentation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and comprised approximately 0.4% of the total virion protein. The activity was classified as a cyclic nucleotide-independent protein kinase as it was not effected by cyclic adenosine 3':5'-monophosphate, cyclic guanosine 3':5'-monophosphate, or inhibited by a cyclic nucleotide-dependent protein kinase inhibitor protein, and utilized GTP as well as ATP as a phosphate donor. The greatest rates of phosphorylation were obtained with acidic phosphoprotein substrates such as casein or phosvitin, although potential physiological substrates for this activity included specific virion polypeptides of frog virus.
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PMID:Purification and properties of a virion protein kinase. 0 56

A triglyceride lipase was extracted from defatted pig adipose tissue powder with dilute ammonia and purified about 230-fold by a combination of ammonium sulfate fractionation, heparin-Sepharose 4B, DEAE-cellulose, and Sephadex G-150 column chromatographies and isoelectrofocusing electrophoresis. The enzyme was distinguishable in physical and kinetic properties from the two previously defined lipases in adipose tissue, lipoprotein lipase, and hormone-sensitive lipase. The purified enzyme was fully active in the absence of serum lipoprotein and was not stimulated by adenosine 3':5'-monophosphate-dependent protein kinase. In marked contrast to the already defined lipases, the enzyme was strongly inhibited by serum albumin. The enzyme had a molecular weigt of about 43,000, a pI of 5.2, and pH optimum of 7.0. The enzyme hydrolyzed triolein to oleic acid and glycerol, and did not exhibit esterase activity. The apparent Km for triolein was 0.05 mM. Physiological roles of this new species of lipase remained to be explored.
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PMID:Partial purification and characterization of a triglyceride lipase from pig adipose tissue. 1 Feb 95

A protein kinase associated with purified virions of avian myeloblastosis BAI strain A was partially purified by ion-exchange chromatography and gel filtration. The transfer of phosphate catalyzed by this enzyme required a divalent metal ion and ATP as phosphate donor. GTP could not be substituted for ATP, and the reaction was unaffected by either cyclic AMP or beef-heart protein-kinase inhibitor. Of the virus and nonvirus proteins tested as phosphate acceptors, only acidic proteins were phosphorylated. In particular, purified preparations of reverse transcriptase from avian myeloblastosis virus did not accept phosphate. The enzyme is a basic protein (pI = 9.3), and, on the basis of molecular sieving through Sephadex G-200 and velocity sedimentation on glycerol gradient, the protein kinase has a molecular weight of 45,000.
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PMID:Protein kinase from avian myeloblastosis virus. 2 25

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).
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PMID:Characterization of cholesterol ester hydrolase activities in rabbit and guinea pig aortas. 3 Apr 61

Addition of acetate to a stationary phase culture of Escherichia coli in glycerol mineral salts medium containing phosphorus-32-labeled orthophosphate results in rapid loss of isocitrate dehydrogenase activity and concomitant incorporation of phosphorus-32 into the enzyme. This is the first example of protein phosphorylation in a bacterium in which the endogenous substrate for the protein kinase has been identified.
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PMID:Phosphorylation of Isocitrate dehydrogenase of Escherichia coli. 3 15

Quantitative studies of the action of theophylline and papaverine were performed in rat epididymal fat pads, both on the lipolytic effect and on the activity of phosphodiesterase, adenylate cyclase and protein kinase. Papaverine, a stronger inhibitor of phosphodiesterase than theophylline, did not produce lipolysis. The maximum lipolytic effect (glycerol release) of theophylline was much higher than that of epinephrine and nearly approached the effect exerted by dibutyryl cyclic AMP. While theophylline potentiated or was without any effect on lipolysis produced by epinephrine and dibutyryl cyclic AMP, papaverine at concentration 10- minus 3 M reduced the effect of both drugs as well as of theophylline by 90 per cent. These concentrations of papaverine also strongly inhibited the activity of adenylate cyclase. Neither papaverine nor theophylline prevented the activation of protein kinase by cyclic AMP. The data suggest that the lack of a lipolytic effect of papaverine migth be caused by a combination of its inhibitory effect on adenylate cyclase and direct inhibition of activation of triglyceride lipase.
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PMID:The absence of stimulation of lipolysis by papaverine, a strong inhibitor of phosphodiesterase. 16 81

There appear to be two classes of protein kinases in rat heart and adipose tissue, types I and II. Type I elutes from DEAE-cellulose at smaller than 0.1 M NaCl and type II at greater than 0.1 M NaCl. The type I enzyme is more readily dissociated by salt or histone than is the type II enzyme. If the type I kinase is first dissociated by cAMP, the subunits reassociate very slowly at 0 degrees C on removal of the cAMP by Sephadex G-25 chromatography, whereas those of type II reassociate very rapidly. Rat heart contains mostly type I and a small amount of type II enzyme, whereas adipose tissue contains almost exclusively the type II enzyme. The adipose tissue enzyme resembles the heart type II kinase in all of the above properties, although the two enzymes are not identical as indicated by slight differences in elution patterns from DEAE-cellulose columns. Incubation of rat epididymal adipose tissue with low concentrations of epinephrine (0.11 muM) increases glycerol production and the fraction of the protein kinase in the active form (activity ratio). The change in cAMP under these conditions is not statistically significant. The presence of insulin inhibits the epinephrine effect on glycerol production and protein kinase but has no measurable effect on cAMP levels. Incubation of adipose tissue with high epinephrine concentrations (11 muM) increases the cAMP level, the protein kinase activity ratio, and glycerol production. Under these conditions insulin decreases the cAMP level and kinase activity ratio but does not reduce glycerol production. The data suggest that very small changes in the tissue cAMP level, undetectable by the assay method, are magnified during the stepwise activation of glycerol output aided possibly by cooperative effects between cAMP and protein kinase. The procedure developed for determining the state of activation of the cAMP-dependent protein kinase in adipose tissue must be modified by reducing the salt concentration of the buffers in order to carry out similar studies in the heart. This reflects the different types of protein kinase in the two tissues. The addition of charcoal to crude extracts of heart prevents protein kinase activation by added cyclic AMP. Charcoal should therefore prevent any activation that could occur if any sequestered cAMP were released during homogenization. Charcoal addition thereby provides a means to distinguish intracellular cAMP activation of the kinase from that which might occur following cell rupture. If epinephrine-perfused hearts are homogenized in the presence of charcoal, epinephrine stimulation of the protein kinase is only slightly decreased. This indicates that the protein kinase is activated intracellularly by cAMP and suggests that all of the cAMP in the cell is available to the protein kinase; i.e., cAMP is not released during homogenization.
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PMID:Hormonal regulation of adenosine 3',5'-monophosphate-dependent protein kinase. 16 70

Guanosine 3':5'-cyclic monophosphate (cGMP)-dependent protein kinase has been purified to homogeneity from bovine lung by affinity chromatography and characterized. Partially purified protein kinase, specifically activated by low concentrations of cGMP (22 NM), was adsorbed onto 8-(2-aminoethyl)-amino-adenosine 3':5'-cyclic monophosphate-Sepharose. After washing to remove nonspecific proteins, cGMP-dependent protein kinase was specifically eluted by 0.1 mM cGMP. The purified protein contained cGMP-dependent protein kinase and specific cGMP binding activities. Purification of the holoenzyme was possible because subunit dissociation does not occur upon cyclic nucleotide binding. cGMP-dependent protein kinase holoenzyme has an apparent molecular weight of 150,000 as determined by glycerol density gradient sedimentation. On sodium dodecyl sulfate/polyacrylamide gel electrophoresis, a single protein band of 71,000 molecular weight was observed that suggested the holoenzyme is a dimer composed of subunits of identical molecular weight. cGMP-dependent protein kinase required high concentrations of Mg+2 for optimal activity; a heat-stable protein kinase modulator which inhibited adenosine 3':5'-cyclic monophosphate-dependent protein kinase activity had no effect on the activity of purified cGMP-dependent protein kinase.
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PMID:Purification and characterization of 3':5'-cyclic GMP-dependent protein kinase. 18 78

The time course for epinephrine stimulation of lypolysis, cyclic AMP accumulation and activation of protein kinase was studied in adipose tissue from hypophysectomized rats. Triglyceride breakdown, as assessed by glycerol release, increased rapidly in response to epinephrine, maintained a constant rate as long as the hormone was present, and decreased rapidly to basal values when the hormone was removed. Cyclic AMP accumulation was transient peaking within 3 min of exposure to epinephrine and then declining to levels indistinguishable from basal by 9 min. Protein kinase activity in extracts also peaked at 3 min and thereafter declined to a level approximately 25% greater than resting activity. Peak levels of cyclic AMP, steady state levels of protein kinase activity and the rate of glycerol production were all related in a dose dependent manner to the concentration of epinephrine. These observations suggest that the spike in cyclic AMP levels may be necessary to trigger the activation of lipolysis, but was not sufficient to sustain an accelerated rate of triglyceride breakdown. Continued activation of protein kinase, however, may be essential to sustained lipolysis.
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PMID:Studies on the mechanisms of epinephrine stimulation of lypolysis. 18 36

The addition of norepinephrine to brown fat in vitro produced a dose-dependent increase in the protein kinase activity ratio (the ratio of activity assayed without cAMP to that assayed with cAMP) in extracts subsequently prepared in the presence of 0.5 M NaCl. The ratio was slightly increased by insulin. The effects of norepinephrine were potentiated by theophylline and reduced by propranolol. There was a significant linear regression between protein kinase activity ratio and the rate of glycerol release for ratios between 0.32 and 0.52. Higher activity ratios were associated with a slight but nonsignificant increase in glycerol release. The relationship between the protein kinase activity ratio and the concentration of cAMP in brown fat could be expressed by simple saturation kinetics. There was a significant linear regression between the reciprocal of the concentration of cAMP in the tissue and the reciprocal of the activity ratio over the whole range of observed values. Exposure of 1-month-old rats to cold increased the protein kinase activity ratio in their brown fat. This confirms that activation of protein kinase is involved in the physiological response of a tissue to a specific environmental stimulus. As the rat became fully adapted to the cold, the activity ratio declined. The protein kinase activity ratio in brown fat was low in late fetuses but greatly increased immediately after birth and remained high for the next 2 weeks. During this period the ratio was not further increased by the injection of norepinephrine but was reduced after chemical sympathectomy. The activity ratio in brown fat fell during the 3rd and 4th weeks after birth. At this time injection of norepinephrine increased the ratio whereas chemical sympathectomy had little effect. These observations confirm that the stimulation of the tissue by the sympathetic nerves results in an activation of protein kinase and reflect the reduced requirement for heat production in brown fat as the animals grow.
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PMID:Portein kinases in brown adipose tissue of developing rats. State of activation of protein kinase during development and cold exposure and its relationship to adenosine 3':5'-monophosphate, lipolysis, and heat production. 19 Feb 18


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