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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycogen phosphorylase (alpha-1,4-glucan:orthophosphate D-glucosyltransferase, EC 2.4.1.1) is the rate-determining enzyme catalyzing glycogen degradation. Human brain has been demonstrated previously to express genes of both the liver and muscle isozymes of glycogen phosphorylase. In this report, a human fetal brain cDNA and genomic DNA corresponding to the brain isozyme of glycogen phosphorylase were isolated and characterized. Transcripts corresponding to this isozyme are present in human adult and fetal brain, and at low levels in other human fetal tissues. The predicted C-terminal sequence of the protein encoded by this cDNA and gene differ from that encoded by a phosphorylase cDNA isolated from a human astrocytoma cell line.
Brain Res Mol Brain Res 1989 Nov
PMID:Human brain glycogen phosphorylase: characterization of fetal cDNA and genomic sequences. 261 94

In yeast cells, the activity of glycogen phosphorylase is regulated by cyclic AMP-mediated phosphorylation of the enzyme. We have previously cloned the gene for glycogen phosphorylase (GPH1) in Saccharomyces cerevisiae. To assess the role of glycogen and phosphorylase-catalyzed glycogenolysis in the yeast life cycle, yeast strains lacking a functional GPH1 gene or containing multiple copies of the gene were constructed. GPH1 was found not to be an essential gene in yeast cells. Haploid cells disrupted in GPH1 lacked phosphorylase activity and attained higher levels of intracellular glycogen but otherwise were similar to wild-type cells. Diploid cells homozygous for the disruption were able to sporulate and give rise to viable ascospores. Absence of functional GPH1 did not impair cells from synthesizing and storing trehalose. Increases in phosphorylase activity of 10- to 40-fold were detected in cells carrying multiple copies of GPH1-containing 2 microns plasmid. Northern (RNA) analysis indicated that GPH1 transcription was induced at the late exponential growth phase, almost simultaneous with the onset of intracellular glycogen accumulation. Thus, the low level of glycogen in exponential cells was not primarily maintained through regulating the phosphorylation state of a constitutive amount of phosphorylase. GPH1 did not appear to be under formal glucose repression, since transcriptional induction occurred well in advance of glucose depletion from the medium.
Mol Cell Biol 1989 Apr
PMID:Molecular analysis of GPH1, the gene encoding glycogen phosphorylase in Saccharomyces cerevisiae. 265 1

Glycogen phosphorylase plays a central role in the mobilization of carbohydrate reserves in a wide variety of organisms and tissues. While rabbit muscle phosphorylase remains the most studied and best characterized of phosphorylases, recombinant DNA techniques have led to the recent appearance of primary sequence data for a wide variety of phosphorylase enzymes. The functional properties of rabbit muscle phosphorylases are reviewed and then compared to properties of phosphorylases from other tissues and organisms. Tissue expression patterns and the chromosomal localization of mammalian phosphorylases are described. Differences in functional properties among phosphorylases are related to new structural information. Evolutionary relationships among phosphorylases as afforded by comparative analysis of proteins and gene sequences are discussed.
Crit Rev Biochem Mol Biol 1989
PMID:The family of glycogen phosphorylases: structure and function. 266 96

Selected biochemical parameters of the ventricular myocardium were compared among several orders of adult mammals with established differences in resting heart rate (cattle, 51 beats/min; swine, 68; canine, 107; rabbit, 256; guinea-pig, 273; rat, 355; mouse, 475). It was hypothesized that the biochemical character of mammalian myocardia is associated with the chronic functional demand on the muscle. Therefore, differences observed in the myocardial biochemical potential among the species could reflect differences in resting heart rate. Myocardia from smaller mammals with higher resting heart rate had significantly (P less than 0.05) higher maximal activities of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, lactate dehydrogenase (muscle/total), hexokinase and oxidation rates of glucose and palmitate than did larger mammals with lower resting heart rate. Maximal activities of phosphorylase and phosphofructokinase were more uniform across the animals. Correlation coefficients determined among average values of measured biochemical parameters and resting heart rate indicated that resting heart rate was closely associated with: citrate synthase (r = 0.86), 3-hydroxyacyl-CoA dehydrogenase (r = 0.93), ratio muscle/total lactate dehydrogenase (r = 0.89), hexokinase (r = 0.89), glucose oxidation (r = 0.88), and palmitate oxidation (r = 0.93). Significant correlations were observed among all of these parameters with the exception of citrate synthase vs. 3-hydroxyacyl-CoA dehydrogenase, and glucose oxidation vs. muscle/total lactate dehydrogenase. It was concluded that the oxidative capacity of mammalian myocardia was closely associated with resting heart rate, whereas the glycolytic potential of the myocardia was more uniform among the species.
J Mol Cell Cardiol 1989 Apr
PMID:Biochemical characteristics of mammalian myocardia. 274 58

It has been shown previously that compensatory hypertrophy of the plantaris muscle in adult rats can be induced by surgical removal of the synergistic gastrocnemius muscle. During hypertrophy, muscle transformation also occurs and there is a shift in the fiber type population of the muscle from fast to slow. Towards obtaining a better understanding of the molecular mechanisms controlling this process, we have carried out a kinetic analysis of the change in expression of two muscle-specific genes encoding the slow beta-heavy chain isoform of myosin and the muscle isoform of glycogen phosphorylase. This analysis indicated that significant increases (2-3 fold) in the steady-state levels of slow myosin heavy chain mRNA and protein did not occur until several weeks following ablation of the gatrocnemius muscle. Increases in slow fiber type paralleled the change in beta-myosin heavy chain expression. In contrast, the activity of phosphorylase, as well as the level of its corresponding mRNA, decreased approx. 1.5-2 fold shortly after (2-4 days) ablation of the gastrocnemius and levels remained low for at least several weeks. Significant changes in expression of these genes did not occur in plantaris muscle from sham operated contralateral legs. These studies indicated that changes in the expression of both genes was governed primarily by accumulation of their mRNAs. However, these genes were not coordinately regulated, indicating either that multiple control mechanisms regulate gene expression in this system or that the same controlling factor(s) regulates expression of these genes in temporally different ways.
Mol Cell Biochem 1989 Apr 11
PMID:The genes for beta-myosin heavy chain and glycogen phosphorylase are discoordinately regulated during compensatory growth of plantaris muscle in the adult rat. 277 Jul 9

We have recently demonstrated that the activity of liver glycogen phosphorylase, the rate-limiting enzyme of glycogenolysis, is elevated in genetically diabetic (db/db) mouse and that it is primarily due to the presence of increased amounts of this enzyme. In the present study, we examined the turnover of glycogen phosphorylase in vivo in order to elucidate the mechanism for this specific increase. The rate of phosphorylase synthesis was slightly decreased in the diabetic mouse compared to controls. However, the relative rates of synthesis were similar in these two groups. The rate of degradation of this enzyme was decreased 20% (p less than 0.05) in the diabetic mouse compared to controls. More importantly, the relative rate of degradation of phosphorylase was found to be lower in the diabetic animals. This indicates that the elevated concentration of phosphorylase in the liver of the db/db mouse is likely due to a specific decrease in its rate of degradation.
Mol Cell Biochem 1989 Jun 01
PMID:The rate of degradation of liver glycogen phosphorylase is specifically decreased in the C57BL/KsJ-db/db mouse. 277 Jul 18

Several hepatotoxic agents with varied chemical mechanisms of toxicity (acetaminophen, diquat, and CCl4) depress membrane calcium pumps and/or enhance the permeability of membranes to calcium. To probe the relevance of these findings to maintenance of calcium homeostasis after toxins in vivo, we measured the activity of glycogen phosphorylase a, as an index of cytosolic free [Ca2+], in freeze-clamped liver samples obtained at several times after the toxin dose. Both acetaminophen and diquat caused significant increases of phosphorylase a activity, and activity remained elevated for several hours after the dose. Significantly, the administration prior to diquat of desferrioxamine, which offers protection against the liver necrosis and depression of microsomal Ca2+ accumulation observed after diquat alone (Tsokos-Kuhn et al., Mol Pharmacol 34: 209-214, 1988), decreased phosphorylase activation. Activation of phosphorylase was observed also after CCl4 administration, as previously reported by Long and Moore (Biochem Pharmacol 35: 4131-4137, 1986). We conclude that perturbations in liver membrane Ca2+ regulation observed after administration of these hepatotoxins in vivo correlate directly with phosphorylase a activity, thereby providing additional in vivo evidence for an alteration of Ca2+ homeostasis early in the development of the liver damage produced by these chemicals.
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PMID:Evidence in vivo for elevation of intracellular free Ca2+ in the liver after diquat, acetaminophen, and CCl4. 278 60

Inhibitor-1 following phosphorylation by protein kinase A inhibits phosphoprotein phosphatase-1. We have found that in the rat heart inhibitor-1 is present only in the cytosolic fraction and that its phosphorylation in ventricular slices was increased by isoproterenol but not by isoproterenol and propranolol together. Cardiac microsomal phosphoprotein phosphatase activity, with added phosphorylase a as the substrate, was inhibited 33% by phosphorylated inhibitor-1. Phosphorylated inhibitor-1 decreased the dephosphorylation by exogenous phosphoprotein phosphatase-1 of phospholamban present in the sarcoplasmic reticulum membranes. These results suggest an interaction of cytoplasmic inhibitor-1 with either cytoplasmic or membrane-bound phosphoprotein phosphatase-1 with a subsequent effect on the level of phosphorylated phospholamban and the probable involvement of this interaction in the cardiac response to beta-adrenergic hormones.
Mol Cell Endocrinol 1988 Jan
PMID:A regulation of the level of phosphorylated phospholamban by inhibitor-1 in rat heart preparations in vitro. 283 40

Cyclic nucleotide analogs were used to study relaxation of pig coronary arteries and guinea pig tracheal smooth muscle in an attempt to determine the roles of cAMP- and cGMP-dependent protein kinases (cA-K and cG-K). In pig coronary artery strips, cGMP analogs were generally more effective than cAMP analogs in promoting relaxation of K+-induced contractions. Significant relaxation of this tissue was caused primarily by those cyclic nucleotide analogs that had high affinities for purified cG-K but not for cA-K. The low potencies of cA-K-specific analogs, as compared with cG-K-specific analogs, could not be readily explained by either unusually high susceptibilities to phosphodiesterases or low partition coefficients. The most potent cGMP analog, 8-(4-chlorophenylthio)-cGMP, exhibited a very slow reversibility of its relaxant effects in the intact tissue, consistent with its strong resistance to hydrolysis by phosphodiesterases measured in vitro. Pig coronaries contained atypically high levels of cGMP and cG-K, implying a potentially important role of this enzyme in smooth muscle function. Carbamylcholine-induced contractions of guinea pig tracheal segments were more sensitive than K+-induced pig coronary artery contractions to relaxation by cyclic nucleotide analogs. Consequently, the number of analogs that could be studied was significantly expanded. The cGMP analogs were again generally more potent, and the effectiveness of both cGMP and cAMP analogs in relaxing this preparation correlated with the Ka of the analogs for in vitro activation of cG-K, but not cA-K. A particularly strong correlation was observed when the effects of analogs modified only at the C-8 position were examined. A known target enzyme of cA-K, phosphorylase, was not activated by cG-K-specific analogs but was activated by high concentrations of the cA-K-specific analogs. Studies using cyclic nucleotide analogs support a role for cG-K, but not for cA-K, in decreasing smooth muscle tone.
Mol Pharmacol 1988 Oct
PMID:Relaxation of vascular and tracheal smooth muscle by cyclic nucleotide analogs that preferentially activate purified cGMP-dependent protein kinase. 284 50

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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