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)

Fru 2,6-P2 was present in isolated foetal hepatocytes at a concentration of 1.6 nmol per g cells. When foetal hepatocytes were exposed to glucagon no changes were observed either in the concentration of Fru 2,6-P2 and lactate release or in the activities of 6-phosphofructo-2-kinase and pyruvate kinase. Incubation of purified 6-phosphofructo-2-kinase with the catalytic subunit of protein kinase did not change the enzyme activity. The inhibition by sn-glycerol 3-phosphate was much lower for the foetal than for adult enzyme. These results suggest that an isoenzyme of 6-phosphofructo-2-kinase in foetal hepatocytes different from that of adult hepatocytes may be present.
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PMID:Fructose 2,6-bisphosphate in isolated foetal hepatocytes. 282 45

The effects of growth phase and carbon source on membrane-associated phosphatidylinositol kinase in cell extracts of Saccharomyces cerevisiae were examined. Phosphatidylinositol kinase activity increased 2- and 2.5-fold in glucose- and glycerol-grown cells, respectively, in the stationary phase as compared with the exponential phase of growth. The increase in phosphatidylinositol kinase activity in the stationary phase of growth correlated with an increase in the relative amounts of phosphatidylinositol 4-phosphate, the product of the reaction. The increase in phosphatidylinositol kinase activity was not due to the presence of water-soluble effector molecules in cell extracts as indicated by mixing experiments. Phosphatidylinositol kinase activity decreased in cell extracts of exponential-phase cells preincubated under phosphorylation conditions which favor cyclic AMP-dependent protein kinase activity. Phosphatidylinositol kinase activity was not affected in cell extracts of stationary-phase cells preincubated under phosphorylation conditions.
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PMID:Regulation of phosphatidylinositol kinase activity in Saccharomyces cerevisiae. 282 27

Gonadotropin-releasing hormone (GnRH) stimulates release of pituitary gonadotropins by activating specific plasma membrane receptors. In the present studies, we have used activators of the Ca2+- and phospholipid-dependent protein kinase (protein kinase C) to probe the binding characteristics of agonist- or antagonist-occupied GnRH receptors in intact cell cultures, using a radioligand receptor assay. Specific binding of [125I-Tyr5,D-Ser(tBu)6,Pro9,NHEt]GnRH (Buserelin), a high-affinity GnRH agonist, was increased to 180% of control in the presence of 150 nM phorbol 12-myristate 13-acetate (PMA) or 100 nM phorbol 12,13-dibutyrate (PDB), and to 125% of control in the presence of 200 microM 1,2-dioctanoylglycerol, after 20 min at 23 degrees C. The PMA effects were associated with apparent increases in both binding affinity and number of binding sites. The effects of protein kinase C activators on Buserelin binding were concentration- and time-dependent and were not seen with 4 alpha-PMA or 1,2-dioctanoyl-3-Cl-glycerol, neither of which activate protein kinase C. In contrast, PMA had no measurable effects on specific binding of a GnRH receptor antagonist, Ac[D-pCl-Phe1,2,D-Trp3,125I-Tyr5,D-Lys6,D-Ala10]GnRH. When cell cultures were pretreated with 100 nM PDB in the absence of GnRH and then washed to remove the phorbol ester, no effects of prior protein kinase C activation were detected upon subsequent addition of Buserelin. However, when PDB pretreatment was carried out in the presence of 0.3 microM GnRH, residual enhancement of Buserelin binding, but not antagonist binding, was observed at either 23 or 4 degrees C. The radiolabeled agonist activated, and the antagonist blocked, GnRH receptor-mediated luteinizing hormone release and [3H]inositol phosphate production in cells preloaded with [3H]inositol. These findings suggest that the action of protein kinase C on the GnRH receptor, either direct or indirect, requires the receptor to be in an activated (agonist-occupied) state but does not require receptor internalization. The mechanism of these effects on GnRH agonist binding is not known but may involve sequestration of surface receptors, expression of new receptors, and/or modulation of GnRH receptor affinity.
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PMID:Differential sensitivity of agonist- and antagonist-occupied gonadotropin-releasing hormone receptors to protein kinase C activators. A marker for receptor activation. 283 Feb 80

Protein kinase C activity was studied in superoxide-producing human polymorphonuclear leukocytes. Using equivalent cell concentrations, superoxide production and particulate fraction-associated protein kinase C activity increased in parallel in phorbol 12-myristate 13-acetate (PMA), oleoyl-acetyl-glycerol (OAG), opsonized zymosan, and A23187-activated leukocytes. Also, an increase in particulate fraction-associated phospholipid-independent kinase activity was observed upon stimulation with these activators. In contrast, in formyl-methionyl-leucine-phenylalanine (FMLP)-activated cells the increase in superoxide production was only accompanied by an increase in particulate fraction-associated protein kinase C activity if the cells were pretreated with cytochalasin B. Purified protein kinase C activity was stimulated by OAG and PMA, whereas no stimulation was observed using A23187 or opsonized zymosan. It is suggested that the activation induced in human neutrophils by PMA, OAG, opsonized zymosan, and A23187 involves a tight membrane association of phospholipid-dependent and -independent protein kinase activity. This contrasts to FMLP-activated neutrophils, in which a membrane-bound form is only observed after pretreatment with cytochalasin B.
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PMID:Membrane-associated protein kinase C activity in superoxide-producing human polymorphonuclear leukocytes. 283 89

6-Phosphofructo-2-kinase was purified from rat liver and hepatoma (HTC) cells. The HTC cell enzyme had kinetic properties different from those of the liver enzyme (more sensitive to inhibition by citrate and not inhibited by sn-glycerol 3-phosphate) and was not a substrate of the cyclic-AMP-dependent protein kinase. Unlike the liver enzyme, which is bifunctional and phosphorylated by fructose 2,6-[2-32P]bisphosphate, the HTC cell enzyme contained no detectable fructose-2,6-bisphosphatase activity and phosphorylation by fructose 2,6-[2-32P]-bisphosphate could not be detected. HTC cell fructose-2,6-bisphosphatase could be separated from 6-phosphofructo-2-kinase activity by purification. Antibodies raised against liver 6-phosphofructo-2-kinase did not precipitate HTC cell fructose-2,6-bisphosphatase whose kinetic properties were completely different from those of the liver enzyme.
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PMID:Rat hepatoma (HTC) cell 6-phosphofructo-2-kinase differs from that in liver and can be separated from fructose-2,6-bisphosphatase. 284 Nov 25

A protein kinase, termed microtubule-associated protein (MAP) kinase, which phosphorylates microtubule-associated protein 2 (MAP-2) in vitro and is stimulated 1.5-3-fold in extracts from insulin-treated 3T3-L1 cells has been identified (Ray, L.B., and Sturgill, T.W. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 1502-1506). Here, we describe chromatographic properties of MAP kinase and provide biochemical characterization of the partially purified enzyme. Isolation of the enzyme is facilitated by its unusually high affinity for hydrophobic interaction chromatography matrices. The molecular weight of the partially purified enzyme was determined to be 35,000 by gel filtration chromatography and 37,000 by glycerol gradient centrifugation. MAP kinase activity of chromatographic fractions correlated precisely with the presence of a 40-kDa phosphoprotein detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. MAP kinase has a Km of 7 microM for ATP and does not utilize GTP. Acetyl-CoA carboxylase, ATP citrate-lyase, casein, histones, phosvitin, protamine, and ribosomal protein S6 were all poor substrates relative to MAP-2. The enzyme is inhibited by fluoride and beta-glycerol phosphate but not by heparin. These properties of MAP kinase distinguish it from protein kinases previously described in the literature.
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PMID:Characterization of insulin-stimulated microtubule-associated protein kinase. Rapid isolation and stabilization of a novel serine/threonine kinase from 3T3-L1 cells. 284 41

Activation of glycolysis by insulin in cultured adult rat hepatocytes is accompanied by an activation of phosphofructokinase 2 (PFK 2). PFK 2 activation might be caused by insulin-dependent changes of (a) metabolite levels, (b) basal and (c) Br8cAMP-stimulated cAMP-dependent protein kinase activity; this problem was investigated. 1. Cells cultured with 0.1 nM insulin for 48 h exhibited a low glycolytic rate and low fructose 2,6-bisphosphate [Fru(2,6)P2] levels. Addition of insulin increased Fru(2,6)P2 and Fru(1,6)P2 levels sequentially which points to PFK 2 as first target enzyme of insulin action. 2. Concentrations of Glc6P, Fru6P, phosphoenolpyruvate, glycerol 3-phosphate and citrate, which modulate PFK 2/fructose 2,6-bisphosphatase 2 activity, were not altered by insulin. 3. Activation of PFK 2 by insulin occurred without changes in the levels of total and protein-bound cAMP. Bound cAMP amounted to about 14% of total cAMP. 4. Insulin neither decreased the basal dissociation state of the cAMP-dependent protein kinase nor lowered the sensitivity of the kinase towards cAMP in cell extracts. 5. Addition of the phosphodiesterase-resistant Br8cAMP to the cultures increased cAMP levels 3-4-fold, elevated the protein kinase activity ratio from 0.14 to 0.6 and decreased the Fru(2,6)P2 level and the rate of glycolysis. When Br8cAMP and insulin were given together, insulin was capable of counteracting Br8cAMP in that it activated glycolysis and PFK 2 and elevated the Fru(2,6)P2 level; however, it did not decrease the elevated protein kinase activity ratio. It is concluded that insulin presumably does not activate PFK 2 through changes in cAMP and effector levels or through inhibition of cAMP-dependent protein kinase dissociation. The data support the hypothesis that insulin may act via activation of PFK 2 phosphatase.
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PMID:Activation of phosphofructokinase 2 by insulin in cultured hepatocytes without accompanying changes of effector levels or cAMP-stimulated protein kinase activity ratios. 284 74

Previous studies have identified the protein product of v-rel, the oncogene carried by reticuloendotheliosis virus (REV), as a 59,000-dalton phosphoprotein located predominantly in the cytosol of transformed chicken lymphoid cells. In immune precipitates of p59v-rel, there is a closely associated protein kinase activity. In chicken lymphoid cells that do not contain REV, p68c-rel is found free in the cytosol not associated with other proteins and not detectably phosphorylated. In this study, we found that immune precipitates of 59v-rel from REV-transformed cells contain at least four other proteins, of approximate molecular weights 124, 115, 68, and 36 kilodaltons (kDa). The 124-, 115-, and 36-kDa proteins are apparently unrelated to p59v-rel in sequence, and their coprecipitation suggests that they are complexed with p59v-rel. The coprecipitating 68-kDa protein was found to be p68c-rel, which, like the other three proteins, precipitates by virtue of its association with p59v-rel. Glycerol gradient analysis suggested the presence of more than one type of complex: one containing p115, p68c-rel, p59v-rel, and p36, and another containing p124, p115, p59v-rel, and possibly p68c-rel. In vitro kinase activity was found in all size classes, coinciding with the distribution of p115 and p59v-rel. The complex(es) was stable under a variety of conditions, including a wide range of ionic strengths, chelators, and detergents, and through multiple cycles of immune precipitation and elution. This suggests a specific and functionally significant interaction among the members that may be of direct relevance to the mechanism of REV-induced transformation.
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PMID:p59v-rel, the transforming protein of reticuloendotheliosis virus, is complexed with at least four other proteins in transformed chicken lymphoid cells. 284 83

In ovarian follicles of Rana pipiens, frog pituitary homogenates (FPH) elevate intrafollicular progesterone levels which in turn is thought to induce meiotic resumption in the prophase I arrested oocytes. Calcium plays a role in FPH and steroid-provoked responses in the somatic and gametic components of the follicle, presumably via effects exerted at the plasma membrane of their respective target cells. Many membrane active hormones which utilize Ca2+ in their intracellular transduction also provoke membrane phosphoinositide hydrolysis yielding inositol triphosphate (IP3) and diacyl glycerol (DAG), an activator of the CA2+-dependent protein kinase C (PKC). The actions of phorbol 12-myristate 13-acetate (TPA), a potent synthetic activator of PKC, on progesterone production and oocyte maturation was examined in in vitro cultured ovarian follicles. TPA induced germinal vesicle breakdown (GVBD) in intact follicles and in oocytes denuded of somatic components, while the inactive compound phorbol 13-monoacetate was ineffective. Further, TPA induction of GVBD exhibited similarities to progesterone-induced GVBD, being inhibited by treatments which elevate cAMP or inhibit protein synthesis. TPA alone did not elevate intrafollicular or medium progesterone levels, as occurred in FPH-treated follicles. TPA partially inhibited intrafollicular progesterone accumulation induced by FPH or treatments which elevate cAMP levels. These data suggest that activation of PKC plays a role in oocyte maturation independent of follicular progesterone production as occurs in response to FPH. Further, it appears that the somatic cells of the amphibian follicle also possess PKC which when activated, antagonizes cAMP generating pathway in these cells. Results indicate that protein kinase can influence oocyte maturation in Rana follicular oocytes by several mechanisms.
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PMID:Role of protein kinase C activation in oocyte maturation and steroidogenesis in ovarian follicles of Rana pipiens: studies with phorbol 12-myristate 13-acetate. 285 34

The influence of tumour promoters and growth factors on glycolysis and on fructose-2,6-bisphosphate concentration was studied in isolated mouse spleen lymphocytes and in purified B-cells. The intracellular concentration of fructose 2,6-bisphosphate and the rate of lactate release were increased 2-3-fold in spleen lymphocytes exposed to active phorbol esters, mitogenic lectins, interleukin 4 or lipopolysaccharide. The maximal effect was observed after 1 h of exposure. In these cells hexose 6-phosphates increased 2-fold and 6-phosphofructo-2-kinase activity remained unchanged after treatment with phorbol 12,13-dibutyrate or with lectins. Exposure of B-cells to phorbol 12,13-dibutyrate, interleukin 4 or lipopolysaccharide increased the glycolytic flux and the concentration of fructose 2,6-bisphosphate without relation to their mitogenic activity. Lymphocytes and rat liver 6-phosphofructo-2-kinase were partially purified using the same procedure. The lymphocyte enzyme was not inhibited by sn-glycerol 3-phosphate in contrast to the potent inhibition observed in liver. Treatment of both enzymes with the catalytic subunit of the cyclic-AMP-dependent protein kinase failed to inactivate 6-phosphofructo-2-kinase from lymphocytes. These differences suggest that lymphocytes and liver contain different forms of this enzyme.
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PMID:Phorbol 12,13-dibutyrate and mitogens increase fructose 2,6-bisphosphate in lymphocytes. Comparison of lymphocyte and rat-liver 6-phosphofructo-2-kinase. 296 4


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