Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Limited proteolysis of catalytic and regulatory subunits of cyclic AMP-dependent protein kinase (A-pk), cyclic AMP phosphodiesterase, glycogen synthase, and histones by fungal protease (type XIX) was analyzed by the digested peptide bands in SDS polyacrylamide gel electrophoresis. The modulatory effects on proteolysis by nucleotides, polypeptides, and phospholipids may greatly depend on the intrinsic nature of substrates. The proteolysis of the regulatory subunit of A-pk and glycogen synthase was not regulated by nucleotides and nucleic acids. In comparison, phosphatidyl serine, cardiolipin, and pepstatin A stimulated the proteolysis of the catalytic subunit of A-pk. Whereas, lambda DNA (Hind III digest), t-RNA, GTP-, phosphatidyl serine, sphingosine inhibited the proteolysis of cyclic AMP phosphodiesterase. Moreover, MS2 RNA, lambda DNA, t-RNA, dGTP, Phosphatidyl serine, phosphatidyl inositol, antipain, and chymostatin exerted inhibitory proteolytic effect on histone VIII-S. Some of these agents also had similar inhibitory effect on other types of histones (types III-S and VII-S). The inhibitory effect of phosphatidyl serine on proteolysis of histone may be due to their interaction which was monitored by the drastic increase of uv absorbance.
Mol Cell Biochem 1991 Apr 10
PMID:Regulation of fungal proteolysis on cyclic AMP-dependent protein kinase, cyclic AMP phosphodiesterase, glycogen synthase and histones. 165 82

The catalytic (alpha) subunit of casein kinase II from Drosophila, cloned and expressed in Escherichia coli (Saxena, A., Padmanabha, R., and Glover, C. V. C., (1987) Mol. Cell. Biol. 7, 3409-3417), has been purified and characterized, and the properties have been compared to those of the holoenzyme. The catalytic subunit exhibits protein kinase activity with casein as substrate and is autophosphorylated. The specific activity of the purified subunit is 6% of the activity of the holoenzyme from reticulocytes or from Drosophila. The alpha subunit is a monomer, eluting at Mr = 40,000 upon gel filtration in high salt, but as part of an aggregate in low salt. The alpha subunit has been purified to apparent homogeneity by sequential chromatography on DEAE-cellulose, Mono S, and Mono Q. A single band, Mr = 37,000, is detected by silver staining following polyacrylamide gel electrophoresis. The isolated alpha subunit displays apparent Km values for beta casein, ATP, and GTP similar to those of the holoenzyme. The activity of the alpha subunit is inhibited by heparin with an I50 of 0.1-0.3 micrograms/ml, a value similar to that observed for the holoenzyme; autophosphorylation is also inhibited by heparin. Polylysine has no stimulatory effect on the activity of the catalytic subunit, as measured with casein and by autophosphorylation, but stimulates both activities with the holoenzyme. When physiological substrates for casein kinase II are examined, glycogen synthase and eukaryotic initiation factor 3 (eIF-3) (p120) are phosphorylated by the alpha subunit at a rate equivalent to that of the holoenzyme, while phosphorylation of eIF-3 (p67) is reduced 9-fold and eIF-2 beta is not modified. From these data, it can be concluded that the alpha subunit of casein kinase II is sufficient for catalysis, is autophosphorylated, and can be directly inhibited by heparin, whereas the beta subunit mediates the effects of basic stimulatory compounds and is involved in recognition and/or binding to specific physiological substrates.
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PMID:Characterization of the catalytic subunit of casein kinase II expressed in Escherichia coli and regulation of activity. 190 Aug 38

The human insulin receptor (hIR) is expressed in two variant forms that are generated by tissue-specific alternative splicing of the 11th exon of the IR gene. This leads to receptors that differ in their affinities for insulin based on the absence (hIR-A) or presence (hIR-B) of a 12-amino acid insert near the C-terminus of the alpha-subunit. To explore further the functional significance of the difference in these receptor subtypes, the properties of hIR-A(exon 11-) and hIR-B(exon 11+) receptors have been compared in parallel. Despite their different affinities for insulin, the receptor variants retain equivalent acid sensitivity for insulin binding and bind proinsulin with the same relative affinity. Both hIR-A and hIR-B are able to signal a variety of insulin's actions, but the insulin dose-response curves for receptor autophosphorylation and for mitogenesis and glycogen synthase stimulation in cells are shifted to the right for hIR-B receptors compared to hIR-A receptors. The magnitude of these rightward shifts, 1.5- to 3-fold in the assays listed above, are similar to and presumably accounted for by the 2-fold difference in insulin affinity exhibited by the receptor variants. Occupied hIR-A and hIR-B receptors undergo indistinguishable endocytotic itineraries after insulin binding. Both lead to insulin degradation that is quantitatively and kinetically similar, and both down-regulate when exposed to saturating insulin for 24 h. Thus, the functional consequences of the alternative splicing of IRs are limited to those related to the variants' differing affinities for insulin.
Mol Endocrinol 1991 May
PMID:Different ligand affinities of the two human insulin receptor splice variants are reflected in parallel changes in sensitivity for insulin action. 207 30

The enhanced phosphorylations via cAMP, Ca2+ mobilization, and diacyl glycerol formation via the activation of the respective kinases is now classical. The decreased phosphorylation via inhibition of adenylate cyclase via the alpha adrenergic receptor is also becoming understood. What the insulin studies on the control of glycogen synthesis have taught us is that the rate limiting enzyme glycogen synthase is regulated by multiple covalent phosphorylation in an elegant but complex manner. The overall pattern of dephosphorylation is influenced by effecting both phosphatase and kinase activities in a set of interrelated mechanisms. In the presence of glucose, in muscle, fat, and liver under physiological conditions G-6-P acts as a signal to stimulate the phosphatase. An additional stimulation could occur via a novel insulin phosphatase stimulatory mediator. The phosphatase is also stimulated by at least three covalent mechanisms involving altered phosphorylation state. In one there is a decreased phosphorylation of the phosphatase inhibitor 1 potentially related to decreased cAMP-dependent protein kinase activity. In the second, there is decreased phosphorylation of the deinhibitor also potentially related to decreased cAMP-dependent protein kinase phosphorylation. In the third, an increased activity of casein kinase 2 could activate the ATP-Mg dependent phosphatase by an increased phosphorylation of phosphatase inhibitor 2 (modulatory subunit). In the liver, allosteric control of the phosphatase by G-6-P and nucleotides is of great importance. Insulin also stimulates the phosphatase in long-term experiments via increased protein synthesis. It is clear that future work will be required to determine which species of the various classes of phosphatases are regulated in short-term and long-term regulation by insulin. In terms of kinases, the effects of insulin to inactivate and desensitize the cAMP-dependent protein kinase are established. The molecular mechanisms of this effect remain to be worked out. The enhanced activity of MAP and S-6 kinase would appear to be part of a cascade of reactions perhaps originating in the autophosphorylation and activation of the insulin receptor tyrosine kinase. The mechanism of the short-term activation of casein kinase 2 remains to be elucidated. A cAMP-dependent protein kinase inhibitory mediator, which also inhibits adenylate cyclase is an important element in the regulation of kinase and adenylate cyclase activity by insulin. Its physiological significance must be established in the future, in terms of its control of glycogen synthase activation by insulin. Clearly this kinase inhibitor as well as the phosphatase stimulator are potential regulators of glycogen synthase activity by insulin.
Adv Enzymol Relat Areas Mol Biol 1990
PMID:Insulin and the stimulation of glycogen synthesis. The road from glycogen structure to glycogen synthase to cyclic AMP-dependent protein kinase to insulin mediators. 215 10

Glycogen synthase kinase-3 (GSK-3) was purified from rabbit liver to homogeneity by ultracentrifugation, ion-exchange chromatography on DEAE-cellulose, Cellulose phosphate, CM-Sephadex and Fast Protein Liquid Chromatography (FPLC) on Mono-S column. The enzyme was purified approximately 20,000 fold with an approximate 2% recovery. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis. GSK-3 is a monomeric enzyme with a molecular weight of 50,000-52,000 as derived from SDS-polyacrylamide gel electrophoresis and gel filtration. The purified enzyme was indeed a GSK-3 since it phosphorylated three sites, i.e., 3a, 3b, and 3c on liver glycogen synthase. GSK-3 incorporated up to 2.6 mol Pi/mol glycogen synthase subunit with a concomitant inactivation of glycogen synthase activity.
Mol Cell Biochem 1990 Jun 25
PMID:Purification and partial characterization of glycogen synthase kinase-3 from rabbit liver. 216 42

The regulation of glycogen metabolism in Schistosoma mansoni was studied in vitro with special emphasis on the possible occurrence of substrate ('futile') cycling. The partition of label between carbon atoms 1 and 6 of the glucose units in glycogen was analysed after the incubation of intact worm pairs in the presence of [6-14C]glucose. Under all conditions tested, more than 99% of the label in glycogen was still in the 6 position, demonstrating that glycogen was synthesised not via an indirect pathway involving 3-carbon units, but directly, from glucose. Increasing the glucose concentration stimulated glycogen synthase and decreased the activity of glycogen phosphorylase. An inverse relationship was shown between the actual glycogen content and the rate of glycogenesis. Substrate cycling occurred between glucose 6-phosphate and glycogen. Glucose was incorporated into glycogen during periods of net glycogen breakdown, and vice versa: glycogen degradation occurred during periods of net glycogen synthesis. Under our experimental conditions of net glycogen degradation, the rate of glycogen synthesis as a percentage of that of glycogen breakdown was dependent on the external glucose concentration and ranged from 5 to 68% for 2 to 100 mM glucose, respectively. The synthesis of glycogen during periods of net glycogen breakdown was shown to occur in each individual worm pair.
Mol Biochem Parasitol 1990 Feb
PMID:Substrate cycling between glucose 6-phosphate and glycogen occurs in Schistosoma mansoni. 230 87

Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2-15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in Vmax and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1990 Feb 09
PMID:Hepatic glycogen metabolism in the db/db mouse. 240 41

We have studied the effects of insulin on several aspects of cell metabolism in the insulin-sensitive, nonfusing muscle cell line BC3H-1. In the absence of exogenous hexose, insulin did not alter basal glycogen synthase percentage I activity, or attenuate the increase in intracellular cAMP content, the activation of glycogen phosphorylase a, or the decrease in glycogen synthase I brought about by beta-adrenergic receptor activation with epinephrine. In contrast, both insulin and the tumor-promoting phorbol ester, tetradecanoylyl phorbol acetate markedly increased mitochondrial pyruvate dehydrogenase activity in the absence of hexose. Both glycogen synthase phosphatase and glycogen synthase kinase activities were present in BC3H-1 cell extracts and were regulated in the expected manner by glucose 6-phosphate and cAMP, respectively. Since the pattern of partial insulin resistance seen in BC3H-1 myocytes would require that several potentially insulin-sensitive enzymes be insensitive to insulin-generated signals, the most likely explanation for these data is that the myocytes are defective in some mechanism of insulin signaling which is independent of the mechanism for pyruvate dehydrogenase activation.
Mol Pharmacol 1986 Dec
PMID:Hexose-independent activation of glycogen synthase and pyruvate dehydrogenase by insulin is dissociated in the mouse BC3H-1 cell line. 243 Dec 65

In a stop-experiment using the hepatocarcinogen N-nitrosomorpholine, as well as glycogenotic and related lesions, hepatocellular foci with a different histochemical pattern were identified. The outstanding features of these hepatic foci, which may progress to hepatocellular adenoma, were increased activities of mitochondrial glycerol-3-phosphate dehydrogenase (mG3PD), glycogen synthase, pyruvate kinase and glucose-6-phosphatase detected by enzyme histochemistry. Since no decrease in activity of any of the enzymes examined were seen in these foci, compared with normal liver, the term enzymatically hyperactive focus (EHF) is proposed for this type of lesion. Only at the stage of overtly nodular growth did these lesions exhibit some of the characteristic changes seen in nodules developing from glycogenotic foci, namely elevated activities of glucose-6-phosphate dehydrogenase, gamma-glutamyl transferase and glutathione-S-transferase P as well as decreased activities of adenosine-triphosphatase, glucose-6-phosphatase and adenylate cyclase. Some of these enzymes have been used widely in morphometric studies as markers for preneoplastic and neoplastic lesions. The inability to detect early EHF may lead to an underestimation of preneoplastic liver lesions in quantitative studies. Although there are apparent differences in the histochemical patterns of glycogen storing foci and early EHF, these differences tend to disappear during progression to overtly neoplastic lesions. In studies comparing the phenotypic alterations in different types of preneoplastic hepatic lesions, the recognition of EHF may contribute to the distinction of obligatory from facultative phenomena during transformation.
Virchows Arch B Cell Pathol Incl Mol Pathol 1989
PMID:Unusual histochemical pattern in preneoplastic hepatic foci characterized by hyperactivity of several enzymes. 256 54

The actions of cyclic AMP are subject to several levels of post-receptor modulation in cardiac tissue. Isoproterenol and prostaglandin E1 both stimulate cAMP accumulation, but only isoproterenol causes activation of particulate cAMP-dependent protein kinase, leading to activation of phosphorylase kinase and glycogen phosphorylase, and inhibition of glycogen synthase. Through the use of isolated, adult ventricular myocytes, we have determined that the hormone-specific activation of glycogen phosphorylase is due to subcellular compartmentation of cAMP. There is some evidence that cyclic nucleotide phosphodiesterases, whose activity is stimulated by alpha 1-adrenergic agonists in isolated myocytes, may have a role in compartmentation. Phosphoinositide hydrolysis is stimulated by alpha 1 and muscarinic agonists, presumably leading to activation of protein kinase C, which in turn has multiple effects on hormone-sensitive adenylate cyclase.
Mol Cell Biochem
PMID:Post-receptor modulation of the effects of cyclic AMP in isolated cardiac myocytes. 284 10


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