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:2.7.11.11 (AMPK)
12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Highly purified repressible acid phosphatase from Saccharomyces cerevisiae very efficiently dephosphorylates 32P-histones and the phosphopeptides Arg-Arg-Ala-Ser-(32P)-Val-Ala and Arg-Arg-Leu-Ser (32P)-Leu-Arg previously phosphorylated by either cAMP-dependent protein kinase or protein kinase-C. The Km values (0.03-1 microM) are very favourable if compared with those calculated for free phosphoaminoacids and p-nitrophenylphosphate which are three to six orders of magnitude higher. While also the phosphopeptide Asp-Ala-Gly-Tyr(32P)-Ala-Arg3-Gly is readily dephosphorylated, other phosphopeptides and phosphoproteins including phosphorylase kinase, phosvitin and casein phosphorylated by both casein kinase 1 and 2 are not appreciably affected by acid phosphatase. It is suggested that yeast repressible acid phosphatase may act in vivo as a phosphoprotein phosphatase.
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PMID:Repressible acid phosphatase from yeast efficiently dephosphorylates in vitro some phosphorylated proteins and peptides. 389 26

The structure of nonactivated and activated forms of phosphorylase kinase has been investigated. The enzyme activation was achieved by phosphorylation with cAMP-dependent protein kinase as well as by incubation of the enzyme in an alkaline medium (pH 8.8). For structural comparison of the enzymic forms, hydrophobic chromatography on phenyl-Sepharose and polyacrylamide gel electrophoresis were used. It has been shown that the enzyme activation results in a release of a low molecular weight component (Mr 16 000). The properties of this component resemble those of calmodulin. Evidence for the formation of an unstable nonactivated phosphorylase kinase - calmodulin complex may be important for the correct understanding of the mechanism of enzyme activation.
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PMID:Study of properties of phosphorylase kinase using hydrophobic chromatography. 403 13

Dimethyl sulfoxide (DMSO) stimulated the activity of a partially purified tyrosine protein kinase from rat lung. The stimulation was concentration dependent with a maximum stimulation (about 2 fold) observed at 10 per cent (V/V) DMSO. On the other hand, acetone (10 percent, V/V), did not exert any stimulatory effect on the enzyme activity. The stimulation was associated with a decrease in the Km for the substrate and an increase in the Vmax. In contrast, the Km for ATP was not affected by DMSO. Under identical assay conditions, DMSO did not significantly alter the activities of phosphorylase kinase, catalytic subunit of cAMP-dependent protein kinase and Ca2+-phospholipid-dependent protein kinase. It may be speculated that stimulation of tyrosine protein kinase may be one of the mechanisms by which DMSO exerts its biological effects.
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PMID:Stimulation of tyrosine protein kinase activity by dimethyl sulfoxide. 403 77

The main kinetic parameters for purified phosphorylase kinase from chicken skeletal muscle were determined at pH 8.2: Vm = 18 micromol/min/mg; apparent Km values for ATP and phosphorylase b from rabbit muscle were 0.20 and 0.02 mM, respectively. The activity ratio at pH 6.8/8.2 was 0.1-0.4 for different preparations of phosphorylase kinase. Similar to the rabbit enzyme, chicken phosphorylase kinase had an absolute requirement for Ca2+ as demonstrated by complete inhibition in the presence of EGTA. Half-maximal activation occurred at [Ca2+] = 0.4 microM at pH 7.0. In the presence of Ca2+, the chicken enzyme from white and red muscles was activated 2-4-fold by saturating concentrations of calmodulin and troponin C. The C0.5 value for calmodulin and troponin C at pH 6.8 was 2 and 100 nM, respectively. Similar to rabbit phosphorylase kinase, the chicken enzyme was stimulated about 3-6-fold by glycogen at pH 6.8 and 8.2 with half-maximal stimulation occurring at about 0.15% glycogen. Protamine caused 60% inhibition of chicken phosphorylase kinase at 0.8 mg/ml. ADP (3 mM) at 0.05 mM ATP caused 85% inhibition with Ki = 0.2 mM. Unlike rabbit phosphorylase kinase, no phosphorylation of the chicken enzyme occurred in the presence of the catalytic subunit of cAMP-dependent protein kinase. Incubation with trypsin caused 2-fold activation of the chicken enzyme.
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PMID:[Regulatory properties of phosphorylase from chicken skeletal muscle]. 407 75

The dephosphorylation of phosphorylase kinase by four rabbit skeletal muscle protein phosphatases was studied. The four enzymes used were preparations of protein phosphatases C-I, C-II, H-I, and H-II. Phosphatases C-I, C-II, and H-II were obtained as homogeneous preparations using procedures previously developed. Phosphatase H-I was purified 644-fold from rabbit skeletal muscle for the purposes of this study, and was the major phosphorylase phosphatase activity in the tissue extract. Phosphatases C-I and H-I were relatively specific for removal of the beta subunit phosphate of phosphorylase kinase, this occurring at rates approximately 100 times more rapidly than the removal of the alpha subunit phosphate. In contrast, phosphatases C-II and H-II readily dephosphorylated both the alpha and beta subunits, although the alpha subunit phosphate release occurred at rates about twice that of the beta subunit phosphate. These studies show that skeletal muscle contains two phosphatases capable of acting on phosphorylase kinase, and that these have different specificities as represented by phosphatases H-I and C-I on the one hand, and phosphatases C-II and H-II on the other hand. These studies also provided unequivocal evidence that dephosphorylation of the beta subunit of phosphorylase kinase is solely involved in the inactivation of the cAMP-dependent protein kinase-activated enzyme. When autophosphorylated phosphorylase kinase was used as the substrate, the four phosphatases displayed similar general specificities as they did toward the cAMP-dependent protein kinase-activated enzyme. With none of the phosphatases examined was there any evidence that alpha subunit phosphorylation affected the rate of beta subunit dephosphorylation.
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PMID:Dephosphorylation and inactivation of phosphorylase kinase: subunit specificity of rabbit skeletal muscle protein phosphatases. 608 41

Adrenalectomy causes a depressed glycogenolytic response to catecholamines in myocardium. Total phosphorylase activity (a + b) is 20% lower in isolated, perfused hearts from adrenalectomized (ADX) rats compared with hearts from sham-operated (sham) rats even though the basal activity ratios (-AMP/+AMP) do not differ. In response to epinephrine (50 nM), the sham group has a higher activity ratio than the ADX group (0.23 vs. 0.16); the difference in specific activities of phosphorylase a in the two groups is even greater, 87 versus 49 U/mg protein. The glycogen content of the heart is 30% lower in the ADX group. Adrenalectomy does not alter the accumulation of cAMP and activation of cAMP-dependent protein kinase caused by epinephrine. Although rat heart contains a heat-stable phosphatase inhibitor, the activity of this inhibitor, as judged by phosphorylase phosphatase activity, is not altered by epinephrine stimulation or by adrenalectomy. Epinephrine perfusion increases the activity ratios (pH 6.8:8.2) of phosphorylase kinase equally in sham and ADX hearts; however, the specific activities of phosphorylase kinase (basal and hormone-stimulated) at either pH are lower after adrenalectomy. The sensitivity of phosphorylase kinase activity to stimulation by calcium is the same in the sham and ADX groups. A radioimmunoassay for phosphorylase kinase detects 10% less of this enzyme in hearts from adrenalectomized animals. Specific activities at pH 6.8 and 8.2 based on the quantity of phosphorylase kinase detected by radioimmunoassay suggest a lower phosphorylation state in the ADX group. Decreases in quantities of phosphorylase and phosphorylase kinase and enzyme dissociation due to glycogen depletion could all contribute to a depressed glycogenolytic response in the ADX group.
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PMID:Effects of adrenalectomy on activation of glycogen phosphorylase in rat myocardium. 608 85

We recently reported that phospholamban, the activator of the cardiac sarcoplasmic reticulum calcium pump, is phosphorylated by both cAMP-dependent protein kinase and a membrane-bound, Ca2+/calmodulin-dependent phospholamban kinase. Phospholamban kinase and glycogen phosphorylase b kinase share the same substrate specificity. They differ however in that phospholamban kinase exhibits an absolute requirement for exogenous calmodulin. In line with the latter observation, phospholamban kinase is shown in this report to be inhibited by fluphenazine. Lower concentrations of the drug induced an activation of the kinase, presumably by hydrophobic interaction with either membrane phospholipids or integral proteins. Also, phospholamban kinase was found to be totally insensitive to antibodies elicited against phosphorylase kinase. Since antipsychotic drugs fail to inhibit the delta-subunit-dependent activity of phosphorylase kinase, the above findings confirm that the two kinases are distinct molecular entities. After detergent solubilization of the sarcoplasmic reticulum, the phospholamban-ATPase complex remains a substrate for phospholamban kinase activity, which retains the ability to catalyze the phosphorylation of exogenous phosphorylase b. However, the Ca2+ dependence is entirely lost upon solubilization and no kinase activity is retained on calmodulin-Sepharose in the presence of Ca2+ ions. Phospholamban and phosphorylase kinase activities copurify with the pump-phospholamban complex upon fractionation of the solubilized proteins by density gradient ultracentrifugation, suggesting a tight interaction between the ATPase, its activator, and the phospholamban kinase. A tentative schematic representation of this supramolecular assembly is based upon the results described in this and preceding papers.
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PMID:Ca2+/calmodulin-dependent phospholamban kinase from cardiac sarcoplasmic reticulum is distinct from phosphorylase kinase and forms a regulatory complex with phospholamban and the Ca2+-ATPase. 622 Jun 53

Liver glycogen phosphorylase associated with the glycogen pellet was activated by a MgATP-dependent process. This activation was reduced by 90% by ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid, not affected by the inhibitor of the cAMP-dependent protein kinase, and increased 2.5-fold by the catalytic subunit of cAMP-dependent protein kinase. Low levels of free Ca2+ (8 x 10(-8) M) completely prevented the effects of the chelator. The activation of phosphorylase by MgATP was shown not to be due to formation of AMP. DEAE-cellulose chromatography of the glycogen pellet separated phosphorylase from phosphorylase kinase. The isolated phosphorylase was no longer activated by MgATP in the presence or absence of the catalytic subunit of cAMP-dependent protein kinase. The isolated phosphorylase kinase phosphorylated and activated skeletal muscle phosphorylase b and the activation was increased 2- to 3-fold by the catalytic subunit of cAMP-dependent protein kinase. Mixing the isolated phosphorylase and phosphorylase kinase together restored the effects of MgATP and the catalytic subunit of cAMP-dependent protein kinase on phosphorylase activity. These findings demonstrate that the phosphorylase kinase associated with liver glycogen has regulatory features similar to those of muscle phosphorylase kinase.
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PMID:Activation of endogenous phosphorylase kinase in liver glycogen pellet by cAMP-dependent protein kinase. 624 74

Rat liver soluble proteins were phosphorylated by endogenous protein kinase with [gamma-32P]ATP. Proteins were separated in dodecyl sulphate slab gels and detected with the aid of autoradiography. The relative role of cAMP-dependent, cAMP-independent and Ca2+-activated protein kinases in the phosphorylation of soluble proteins was investigated. Heat-stable inhibitor of cAMP-dependent protein kinase inhibits nearly completed the phosphorylation of seven proteins, including L-type pyruvate kinase. The phosphorylation of eight proteins is not influenced by protein kinase inhibitor. The phosphorylation of six proteins, including phosphorylase, is partially inhibited by protein kinase inhibitor. These results indicate that phosphoproteins of rat liver can be subdivided into three groups: phosphoproteins that are phosphorylated by (a) cAMP-dependent protein kinase or (b) cAMP-independent protein kinase; (c) phosphoproteins in which both cAMP-dependent and cAMP-independent protein kinase play a role in the phosphorylation. The relative phosphorylation rate of substrates for cAMP-dependent protein kinase is about 15-fold the phosphorylation rate of substrates for cAMP-independent protein kinase. The Km for ATP of cAMP-dependent protein kinase and phosphorylase kinase is 8 microM and 38 microM, respectively. Ca2+ in the micromolare range stimulates the phosphorylation of (a) phosphorylase, (b) a protein with molecular weight of 130 000 and (c) a protein with molecular weight of 15 000. The phosphate incorporation into a protein with molecular weight of 115 000 is inhibited by Ca2+. Phosphorylation of phosphorylase and the 15 000-Mr protein in the presence of 100 microM Ca2+ could be completely inhibited by trifluoperazine. It can be concluded that calmodulin is involved in the phosphorylation of at least two soluble proteins. No evidence for Ca2+-stimulated phosphorylation of subunits of glycolytic or gluconeogenic enzymes, including pyruvate kinase, was found. This indicates that it is unlikely that direct phosphorylation by Ca2+-dependent protein kinases is involved in the stimulation of gluconeogenesis by hormones that act through a cAMP-independent, Ca2+-dependent mechanism.
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PMID:The role of Ca2+ and cyclic AMP in the phosphorylation of rat-liver soluble proteins by endogenous protein kinases. 625 13

The cAMP-dependent protein kinase catalyzes the phosphorylation of the alpha- and beta-subunits of the cardiac isozyme of phosphorylase kinase. beta-Subunit phosphorylation achieves a maximum level of between 1 to 2 mol of phosphate/mol of phosphorylase kinase, a value less than the stoichiometric content of beta-subunits in the enzyme. This, less than stoichiometric incorporation, is not a result of the presence of endogenous phosphate in equivalent sites in the remaining beta-subunit moieties. Pretreatment of phosphorylase kinase with phosphoprotein phosphatase, under conditions proven to dephosphorylate such sites, does not modify the observed extent of beta-subunit phosphorylation. alpha'-Subunit phosphorylation is initiated at a slower rate than beta but achieves a higher maximum level of incorporation. alpha'-Subunit phosphorylation, but not the extent of beta-subunit phosphorylation, is stimulated by MnCl2 and partially inhibited by NaF; neither is effected by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The activation of cardiac phosphorylase kinase that occurs concomitantly with phosphorylation appears to be dependent upon phosphate incorporation into both the alpha- and beta-subunits. At low levels of activation a close correlation is observed between activation and either alpha-subunit phosphorylation, beta-subunit phosphorylation, or total phosphorylation. However, the cAMP-dependent catalyzed phosphorylation of alpha, at a time after which beta-subunit phosphorylation is already maximal, also results in activation of cardiac phosphorylase kinase.
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PMID:Phosphorylation and activation of the cardiac isoenzyme of phosphorylase kinase by the cAMP-dependent protein kinase. 626 35


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