Glycogen phosphorylase

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Phosphorylase
GlycogenPhosphorylaseDimer.png
The crystal structure of the rabbit muscle glycogen phosphorylase-AMP complex. AMP allosteric site (yellow), phosphorylated Ser14 (orange), glycogen binding site (blue), catalytic site (red). [1]
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EC no. 2.4.1.1
CAS no. 9035-74-9
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Glycogen phosphorylase is one of the phosphorylase enzymes (EC 2.4.1.1). Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. Glycogen phosphorylase is also studied as a model protein regulated by both reversible phosphorylation and allosteric effects.

Contents

Mechanism

Glycogen phosphorylase breaks up glycogen into glucose subunits (see also figure below):

(α-1,4 glycogen chain)n + Pi ⇌ (α-1,4 glycogen chain)n-1 + α-D-glucose-1-phosphate. [2]

Glycogen is left with one fewer glucose molecule, and the free glucose molecule is in the form of glucose-1-phosphate. In order to be used for metabolism, it must be converted to glucose-6-phosphate by the enzyme phosphoglucomutase.

Although the reaction is reversible in vitro, within the cell the enzyme only works in the forward direction as shown below because the concentration of inorganic phosphate is much higher than that of glucose-1-phosphate. [2]

Action of Glycogen Phosphorylase on Glycogen Glycogen phosphorylase stereo.png
Action of Glycogen Phosphorylase on Glycogen

Glycogen phosphorylase can act only on linear chains of glycogen (α1-4 glycosidic linkage). Its work will immediately come to a halt four residues away from α1-6 branch (which are exceedingly common in glycogen). In these situations, the debranching enzyme is necessary, which will straighten out the chain in that area. In addition, the enzyme transferase shifts a block of 3 glucosyl residues from the outer branch to the other end, and then a α1-6 glucosidase enzyme is required to break the remaining (single glucose) α1-6 residue that remains in the new linear chain. After all this is done, glycogen phosphorylase can continue. The enzyme is specific to α1-4 chains, as the molecule contains a 30-angstrom-long crevice with the same radius as the helix formed by the glycogen chain; this accommodates 4-5 glucosyl residues, but is too narrow for branches. This crevice connects the glycogen storage site to the active, catalytic site.

Glycogen phosphorylase has a pyridoxal phosphate (PLP, derived from Vitamin B6) at each catalytic site. Pyridoxal phosphate links with basic residues (in this case Lys680) and covalently forms a Schiff base. Once the Schiff base linkage is formed, holding the PLP molecule in the active site, the phosphate group on the PLP readily donates a proton to an inorganic phosphate molecule, allowing the inorganic phosphate to in turn be deprotonated by the oxygen forming the α-1,4 glycosidic linkage. PLP is readily deprotonated because its negative charge is not only stabilized within the phosphate group, but also in the pyridine ring, thus the conjugate base resulting from the deprotonation of PLP is quite stable. The protonated oxygen now represents a good leaving group, and the glycogen chain is separated from the terminal glycogen in an SN1 fashion, resulting in the formation of a glucose molecule with a secondary carbocation at the 1 position. Finally, the deprotonated inorganic phosphate acts as a nucleophile and bonds with the carbocation, resulting in the formation of glucose-1-phosphate and a glycogen chain shortened by one glucose molecule.

There is also an alternative proposed mechanism involving a positively charged oxygen in a half-chair conformation. [3]

Catalytic Site Mechanism GlycogenPhosphorylaseMechanism.png
Catalytic Site Mechanism

Structure

The glycogen phosphorylase monomer is a large protein, composed of 842 amino acids with a mass of 97.434 kDa in muscle cells. While the enzyme can exist as an inactive monomer or tetramer, it is biologically active as a dimer of two identical subunits. [4]

R and T States of Glycogen Phosphorylase b Tower Helices, on the left and right respectively. Note the relative positioning of the central tower helices, as well as the increased interactions between subunits in the R state. PDB3CEH, PDB3E3O GlycogenPhosphorylaseTandRStates.png
R and T States of Glycogen Phosphorylase b Tower Helices, on the left and right respectively. Note the relative positioning of the central tower helices, as well as the increased interactions between subunits in the R state. PDB3CEH, PDB3E3O

In mammals, the major isozymes of glycogen phosphorylase are found in muscle, liver, and brain. The brain type is predominant in adult brain and embryonic tissues, whereas the liver and muscle types are predominant in adult liver and skeletal muscle, respectively. [5]

The glycogen phosphorylase dimer has many regions of biological significance, including catalytic sites, glycogen binding sites, allosteric sites, and a reversibly phosphorylated serine residue. First, the catalytic sites are relatively buried, 15Å from the surface of the protein and from the subunit interface. [6] This lack of easy access of the catalytic site to the surface is significant in that it makes the protein activity highly susceptible to regulation, as small allosteric effects could greatly increase the relative access of glycogen to the site.

Perhaps the most important regulatory site is Ser14, the site of reversible phosphorylation very close to the subunit interface. The structural change associated with phosphorylation, and with the conversion of phosphorylase b to phosphorylase a, is the arrangement of the originally disordered residues 10 to 22 into α helices. This change increases phosphorylase activity up to 25% even in the absence of AMP, and enhances AMP activation further. [7]

The allosteric site of AMP binding on muscle isoforms of glycogen phosphorylase are close to the subunit interface just like Ser14. Binding of AMP at this site, corresponding in a change from the T state of the enzyme to the R state, results in small changes in tertiary structure at the subunit interface leading to large changes in quaternary structure. [8] AMP binding rotates the tower helices (residues 262-278) of the two subunits 50˚ relative to one another through greater organization and intersubunit interactions. This rotation of the tower helices leads to a rotation of the two subunits by 10˚ relative to one another, and more importantly disorders residues 282-286 (the 280s loop) that block access to the catalytic site in the T state but do not in the R state. [6]

The final, perhaps most curious site on the glycogen phosphorylase protein is the so-called glycogen storage site. Residues 397-437 form this structure, which allows the protein to covalently bind to the glycogen chain a full 30 Å from the catalytic site . This site is most likely the site at which the enzyme binds to glycogen granules before initiating cleavage of terminal glucose molecules. In fact, 70% of dimeric phosphorylase in the cell exists as bound to glycogen granules rather than free floating. [9]

Clinical significance

phosphorylase, glycogen; muscle (McArdle syndrome, glycogen storage disease type V)
Identifiers
SymbolPYGM
NCBI gene 5837
HGNC 9726
OMIM 608455
RefSeq NM_005609
UniProt P11217
Other data
EC number 2.4.1.1
Locus Chr. 11 q12-q13.2
Search for
Structures Swiss-model
Domains InterPro
phosphorylase, glycogen; liver (Hers disease, glycogen storage disease type VI)
Identifiers
SymbolPYGL
NCBI gene 5836
HGNC 9725
OMIM 232700
RefSeq NM_002863
UniProt P06737
Other data
EC number 2.4.1.1
Locus Chr. 14 q11.2-24.3
Search for
Structures Swiss-model
Domains InterPro
phosphorylase, glycogen; brain
Identifiers
SymbolPYGB
NCBI gene 5834
HGNC 9723
OMIM 138550
RefSeq NM_002862
UniProt P11216
Other data
EC number 2.4.1.1
Locus Chr. 20 p11.2-p11.1
Search for
Structures Swiss-model
Domains InterPro

The inhibition of glycogen phosphorylase has been proposed as one method for treating type 2 diabetes. [10] Since glucose production in the liver has been shown to increase in type 2 diabetes patients, [11] inhibiting the release of glucose from the liver's glycogen's supplies appears to be a valid approach. The cloning of the human liver glycogen phosphorylase (HLGP) revealed a new allosteric binding site near the subunit interface that is not present in the rabbit muscle glycogen phosphorylase (RMGP) normally used in studies. This site was not sensitive to the same inhibitors as those at the AMP allosteric site, [12] and most success has been had synthesizing new inhibitors that mimic the structure of glucose, since glucose-6-phosphate is a known inhibitor of HLGP and stabilizes the less active T-state. [13] These glucose derivatives have had some success in inhibiting HLGP, with predicted Ki values as low as 0.016 mM. [14]

Mutations in the muscle isoform of glycogen phosphorylase (PYGM) are associated with glycogen storage disease type V (GSD V, McArdle's Disease). More than 65 mutations in the PYGM gene that lead to McArdle disease have been identified to date. [15] [16] Symptoms of McArdle disease include muscle weakness, myalgia, and lack of endurance, all stemming from low glucose levels in muscle tissue. [17]

Mutations in the liver isoform of glycogen phosphorylase (PYGL) are associated with Hers' Disease (glycogen storage disease type VI). [18] [19] Hers' disease is often associated with mild symptoms normally limited to hypoglycemia, and is sometimes difficult to diagnose due to residual enzyme activity. [20]

The brain isoform of glycogen phosphorylase (PYGB) has been proposed as a biomarker for gastric cancer. [21]

Regulation

Glycogen phosphorylase is regulated through allosteric control and through phosphorylation. Phosphorylase a and phosphorylase b each exist in two forms: a T (tense) inactive state and an R (relaxed) state. Phosphorylase b is normally in the T state, inactive due to the physiological presence of ATP and glucose 6 phosphate, and phosphorylase a is normally in the R state (active). An isoenzyme of glycogen phosphorylase exists in the liver sensitive to glucose concentration, as the liver acts as a glucose exporter. In essence, liver phosphorylase is responsive to glucose, which causes a very responsive transition from the R to T form, inactivating it; furthermore, liver phosphorylase is insensitive to AMP.

Hormones such as epinephrine, insulin and glucagon regulate glycogen phosphorylase using second messenger amplification systems linked to G proteins. Glucagon activates adenylate cyclase through a G protein-coupled receptor (GPCR) coupled to Gs which in turn activates adenylate cyclase to increase intracellular concentrations of cAMP. cAMP binds to and activates protein kinase A (PKA). PKA phosphorylates phosphorylase kinase, which in turn phosphorylates glycogen phosphorylase b at Ser14, converting it into the active glycogen phosphorylase a.

In the liver, glucagon also activates another GPCR that triggers a different cascade, resulting in the activation of phospholipase C (PLC). PLC indirectly causes the release of calcium from the hepatocytes' endoplasmic reticulum into the cytosol. The increased calcium availability binds to the calmodulin subunit and activates glycogen phosphorylase kinase. Glycogen phosphorylase kinase activates glycogen phosphorylase in the same manner mentioned previously.

Glycogen phosphorylase b is not always inactive in muscle, as it can be activated allosterically by AMP. [6] [9] An increase in AMP concentration, which occurs during strenuous exercise, signals energy demand. AMP activates glycogen phosphorylase b by changing its conformation from a tense to a relaxed form. This relaxed form has similar enzymatic properties as the phosphorylated enzyme. An increase in ATP concentration opposes this activation by displacing AMP from the nucleotide binding site, indicating sufficient energy stores.

Upon eating a meal, there is a release of insulin, signaling glucose availability in the blood. Insulin indirectly activates protein phosphatase 1 (PP1) and phosphodiesterase via a signal transduction cascade. PP1 dephosphorylates glycogen phosphorylase a, reforming the inactive glycogen phosphorylase b. The phosphodiesterase converts cAMP to AMP. Together, they decrease the concentration of cAMP and inhibit PKA. As a result, PKA can no longer initiate the phosphorylation cascade that ends with formation of (active) glycogen phosphorylase a. Overall, insulin signaling decreases glycogenolysis to preserve glycogen stores in the cell and triggers glycogenesis. [22]

Historical significance

Glycogen phosphorylase was the first allosteric enzyme to be discovered. [8] It was isolated and its activity characterized in detail by Carl F. Cori, Gerhard Schmidt and Gerty T. Cori. [23] [24] Arda Green and Gerty Cori crystallized it for the first time in 1943 [25] and illustrated that glycogen phosphorylase existed in either the a or b forms depending on its phosphorylation state, as well as in the R or T states based on the presence of AMP. [26]

See also

Related Research Articles

A protein phosphatase is a phosphatase enzyme that removes a phosphate group from the phosphorylated amino acid residue of its substrate protein. Protein phosphorylation is one of the most common forms of reversible protein posttranslational modification (PTM), with up to 30% of all proteins being phosphorylated at any given time. Protein kinases (PKs) are the effectors of phosphorylation and catalyse the transfer of a γ-phosphate from ATP to specific amino acids on proteins. Several hundred PKs exist in mammals and are classified into distinct super-families. Proteins are phosphorylated predominantly on Ser, Thr and Tyr residues, which account for 79.3, 16.9 and 3.8% respectively of the phosphoproteome, at least in mammals. In contrast, protein phosphatases (PPs) are the primary effectors of dephosphorylation and can be grouped into three main classes based on sequence, structure and catalytic function. The largest class of PPs is the phosphoprotein phosphatase (PPP) family comprising PP1, PP2A, PP2B, PP4, PP5, PP6 and PP7, and the protein phosphatase Mg2+- or Mn2+-dependent (PPM) family, composed primarily of PP2C. The protein Tyr phosphatase (PTP) super-family forms the second group, and the aspartate-based protein phosphatases the third. The protein pseudophosphatases form part of the larger phosphatase family, and in most cases are thought to be catalytically inert, instead functioning as phosphate-binding proteins, integrators of signalling or subcellular traps. Examples of membrane-spanning protein phosphatases containing both active (phosphatase) and inactive (pseudophosphatase) domains linked in tandem are known, conceptually similar to the kinase and pseudokinase domain polypeptide structure of the JAK pseudokinases. A complete comparative analysis of human phosphatases and pseudophosphatases has been completed by Manning and colleagues, forming a companion piece to the ground-breaking analysis of the human kinome, which encodes the complete set of ~536 human protein kinases.

<span class="mw-page-title-main">Kinase</span> Enzyme catalyzing transfer of phosphate groups onto specific substrates

In biochemistry, a kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule donates a phosphate group to the substrate molecule. As a result, kinase produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group. These two processes, phosphorylation and dephosphorylation, occur four times during glycolysis.

<span class="mw-page-title-main">Phosphorylation</span> Chemical process of introducing a phosphate

In biochemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology. Protein phosphorylation often activates many enzymes.

<span class="mw-page-title-main">Glucagon</span> Peptide hormone

Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises the concentration of glucose and fatty acids in the bloodstream and is considered to be the main catabolic hormone of the body. It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers extracellular glucose. It is produced from proglucagon, encoded by the GCG gene.

<span class="mw-page-title-main">Protein kinase A</span> Family of enzymes

In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase. PKA has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism. It should not be confused with 5'-AMP-activated protein kinase.

<span class="mw-page-title-main">Glycogenolysis</span> Breakdown of glycogen

Glycogenolysis is the breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase.

<span class="mw-page-title-main">Phosphofructokinase 1</span> Class of enzymes

Phosphofructokinase-1 (PFK-1) is one of the most important regulatory enzymes of glycolysis. It is an allosteric enzyme made of 4 subunits and controlled by many activators and inhibitors. PFK-1 catalyzes the important "committed" step of glycolysis, the conversion of fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP. Glycolysis is the foundation for respiration, both anaerobic and aerobic. Because phosphofructokinase (PFK) catalyzes the ATP-dependent phosphorylation to convert fructose-6-phosphate into fructose 1,6-bisphosphate and ADP, it is one of the key regulatory steps of glycolysis. PFK is able to regulate glycolysis through allosteric inhibition, and in this way, the cell can increase or decrease the rate of glycolysis in response to the cell's energy requirements. For example, a high ratio of ATP to ADP will inhibit PFK and glycolysis. The key difference between the regulation of PFK in eukaryotes and prokaryotes is that in eukaryotes PFK is activated by fructose 2,6-bisphosphate. The purpose of fructose 2,6-bisphosphate is to supersede ATP inhibition, thus allowing eukaryotes to have greater sensitivity to regulation by hormones like glucagon and insulin.

<span class="mw-page-title-main">AMP-activated protein kinase</span> Class of enzymes

5' AMP-activated protein kinase or AMPK or 5' adenosine monophosphate-activated protein kinase is an enzyme that plays a role in cellular energy homeostasis, largely to activate glucose and fatty acid uptake and oxidation when cellular energy is low. It belongs to a highly conserved eukaryotic protein family and its orthologues are SNF1 in yeast, and SnRK1 in plants. It consists of three proteins (subunits) that together make a functional enzyme, conserved from yeast to humans. It is expressed in a number of tissues, including the liver, brain, and skeletal muscle. In response to binding AMP and ADP, the net effect of AMPK activation is stimulation of hepatic fatty acid oxidation, ketogenesis, stimulation of skeletal muscle fatty acid oxidation and glucose uptake, inhibition of cholesterol synthesis, lipogenesis, and triglyceride synthesis, inhibition of adipocyte lipogenesis, inhibition of adipocyte lipolysis, and modulation of insulin secretion by pancreatic β-cells.

<span class="mw-page-title-main">Phosphorylase</span> Class of enzymes

In biochemistry, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor.

Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose levels.

<span class="mw-page-title-main">Glycogen synthase</span> Enzyme class, includes all types of glycogen/starch synthases

Glycogen synthase is a key enzyme in glycogenesis, the conversion of glucose into glycogen. It is a glycosyltransferase that catalyses the reaction of UDP-glucose and n to yield UDP and n+1.

<span class="mw-page-title-main">Glycogen debranching enzyme</span> Mammalian protein found in Homo sapiens

The glycogen debranching enzyme, in humans, is the protein encoded by the gene AGL. This enzyme is essential for the breakdown of glycogen, which serves as a store of glucose in the body. It has separate glucosyltransferase and glucosidase activities.

<span class="mw-page-title-main">Phosphorylase kinase</span>

Phosphorylase kinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen. PhK phosphorylates glycogen phosphorylase at two serine residues, triggering a conformational shift which favors the more active glycogen phosphorylase "a" form over the less active glycogen phosphorylase b.

<span class="mw-page-title-main">Myophosphorylase</span> Muscle enzyme involved in glycogen breakdown

Myophosphorylase or glycogen phosphorylase, muscle associated (PYGM) is the muscle isoform of the enzyme glycogen phosphorylase and is encoded by the PYGM gene. This enzyme helps break down glycogen into glucose-1-phosphate, so it can be used within the muscle cell. Mutations in this gene are associated with McArdle disease, a glycogen storage disease of muscle.

<span class="mw-page-title-main">Sucrose phosphorylase</span> Class of enzymes

Sucrose phosphorylase is an important enzyme in the metabolism of sucrose and regulation of other metabolic intermediates. Sucrose phosphorylase is in the class of hexosyltransferases. More specifically it has been placed in the retaining glycoside hydrolases family although it catalyzes a transglycosidation rather than hydrolysis. Sucrose phosphorylase catalyzes the conversion of sucrose to D-fructose and α-D-glucose-1-phosphate. It has been shown in multiple experiments that the enzyme catalyzes this conversion by a double displacement mechanism.

Enzyme activators are molecules that bind to enzymes and increase their activity. They are the opposite of enzyme inhibitors. These molecules are often involved in the allosteric regulation of enzymes in the control of metabolism. In some cases, when a substrate binds to one catalytic subunit of an enzyme, this can trigger an increase in the substrate affinity as well as catalytic activity in the enzyme's other subunits, and thus the substrate acts as an activator.

<span class="mw-page-title-main">PRKACA</span> Protein-coding gene in the species Homo sapiens

The catalytic subunit α of protein kinase A is a key regulatory enzyme that in humans is encoded by the PRKACA gene. This enzyme is responsible for phosphorylating other proteins and substrates, changing their activity. Protein kinase A catalytic subunit is a member of the AGC kinase family, and contributes to the control of cellular processes that include glucose metabolism, cell division, and contextual memory. PKA Cα is part of a larger protein complex that is responsible for controlling when and where proteins are phosphorylated. Defective regulation of PKA holoenzyme activity has been linked to the progression of cardiovascular disease, certain endocrine disorders and cancers.

<span class="mw-page-title-main">Inborn errors of carbohydrate metabolism</span> Medical condition

Inborn errors of carbohydrate metabolism are inborn error of metabolism that affect the catabolism and anabolism of carbohydrates.

<span class="mw-page-title-main">Protein phosphatase 1</span>

Protein phosphatase 1 (PP1) belongs to a certain class of phosphatases known as protein serine/threonine phosphatases. This type of phosphatase includes metal-dependent protein phosphatases (PPMs) and aspartate-based phosphatases. PP1 has been found to be important in the control of glycogen metabolism, muscle contraction, cell progression, neuronal activities, splicing of RNA, mitosis, cell division, apoptosis, protein synthesis, and regulation of membrane receptors and channels.

Glycogen phosphorylase, liver form (PYGL), also known as human liver glycogen phosphorylase (HLGP), is an enzyme that in humans is encoded by the PYGL gene on chromosome 14. This gene encodes a homodimeric protein that catalyses the cleavage of alpha-1,4-glucosidic bonds to release glucose-1-phosphate from liver glycogen stores. This protein switches from inactive phosphorylase B to active phosphorylase A by phosphorylation of serine residue 14. Activity of this enzyme is further regulated by multiple allosteric effectors and hormonal controls. Humans have three glycogen phosphorylase genes that encode distinct isozymes that are primarily expressed in liver, brain and muscle, respectively. The liver isozyme serves the glycemic demands of the body in general while the brain and muscle isozymes supply just those tissues. In glycogen storage disease type VI, also known as Hers disease, mutations in liver glycogen phosphorylase inhibit the conversion of glycogen to glucose and results in moderate hypoglycemia, mild ketosis, growth retardation and hepatomegaly. Alternative splicing results in multiple transcript variants encoding different isoforms [provided by RefSeq, Feb 2011].

References

  1. ↑ PDB: 3E3N ​
  2. 1 2 Livanova NB, Chebotareva NA, Eronina TB, Kurganov BI (October 2002). "Pyridoxal 5'-phosphate as a catalytic and conformational cofactor of muscle glycogen phosphorylase B". Biochemistry. Biokhimiia. 67 (10): 1089–98. doi:10.1023/A:1020978825802. PMID   12460107. S2CID   12036788.
  3. ↑ Palm D, Klein HW, Schinzel R, Buehner M, Helmreich EJ (February 1990). "The role of pyridoxal 5'-phosphate in glycogen phosphorylase catalysis". Biochemistry. 29 (5): 1099–107. doi:10.1021/bi00457a001. PMID   2182117.
  4. ↑ Browner MF, Fletterick RJ (February 1992). "Phosphorylase: a biological transducer". Trends in Biochemical Sciences. 17 (2): 66–71. doi:10.1016/0968-0004(92)90504-3. PMID   1566331.
  5. ↑ David ES, Crerar MM (January 1986). "Quantitation of muscle glycogen phosphorylase mRNA and enzyme amounts in adult rat tissues". Biochimica et Biophysica Acta (BBA) - General Subjects. 880 (1): 78–90. doi:10.1016/0304-4165(86)90122-4. PMID   3510670.
  6. 1 2 3 Johnson LN (March 1992). "Glycogen phosphorylase: control by phosphorylation and allosteric effectors". FASEB Journal. 6 (6): 2274–82. doi: 10.1096/fasebj.6.6.1544539 . PMID   1544539. S2CID   25954545.
  7. ↑ Newgard CB, Hwang PK, Fletterick RJ (1989). "The family of glycogen phosphorylases: structure and function". Critical Reviews in Biochemistry and Molecular Biology. 24 (1): 69–99. doi:10.3109/10409238909082552. PMID   2667896.
  8. 1 2 Johnson LN, Barford D (February 1990). "Glycogen phosphorylase. The structural basis of the allosteric response and comparison with other allosteric proteins". The Journal of Biological Chemistry. 265 (5): 2409–12. doi: 10.1016/S0021-9258(19)39810-2 . PMID   2137445.
  9. 1 2 Meyer F, Heilmeyer LM, Haschke RH, Fischer EH (December 1970). "Control of phosphorylase activity in a muscle glycogen particle. I. Isolation and characterization of the protein-glycogen complex". The Journal of Biological Chemistry. 245 (24): 6642–8. doi: 10.1016/S0021-9258(18)62582-7 . PMID   4320610.
  10. ↑ Somsák L, Nagya V, Hadady Z, Docsa T, Gergely P (2003). "Glucose analog inhibitors of glycogen phosphorylases as potential antidiabetic agents: recent developments". Current Pharmaceutical Design. 9 (15): 1177–89. doi:10.2174/1381612033454919. PMID   12769745.
  11. ↑ Moller DE (December 2001). "New drug targets for type 2 diabetes and the metabolic syndrome". Nature. 414 (6865): 821–7. Bibcode:2001Natur.414..821M. doi:10.1038/414821a. PMID   11742415. S2CID   4426975.
  12. ↑ Coats WS, Browner MF, Fletterick RJ, Newgard CB (August 1991). "An engineered liver glycogen phosphorylase with AMP allosteric activation". The Journal of Biological Chemistry. 266 (24): 16113–9. doi: 10.1016/S0021-9258(18)98523-6 . PMID   1874749.
  13. ↑ Oikonomakos NG, Kontou M, Zographos SE, Tsitoura HS, Johnson LN, Watson KA, et al. (Jul 1994). "The design of potential antidiabetic drugs: experimental investigation of a number of beta-D-glucose analogue inhibitors of glycogen phosphorylase". European Journal of Drug Metabolism and Pharmacokinetics. 19 (3): 185–92. doi:10.1007/BF03188920. PMID   7867660. S2CID   11168623.
  14. ↑ Hopfinger AJ, Reaka A, Venkatarangan P, Duca JS, Wang S (Sep 1999). "Prediction of Ligand−Receptor Binding Free Energy by 4D-QSAR Analysis: Application to a Set of Glucose Analogue Inhibitors of Glycogen Phosphorylase". Journal of Chemical Information and Computer Sciences. 39 (6): 1141–1150. doi:10.1021/ci9900332.
  15. ↑ Nogales-Gadea G, Arenas J, Andreu AL (January 2007). "Molecular genetics of McArdle's disease". Current Neurology and Neuroscience Reports. 7 (1): 84–92. doi:10.1007/s11910-007-0026-2. PMID   17217859. S2CID   39626196.
  16. ↑ Andreu AL, Nogales-Gadea G, Cassandrini D, Arenas J, Bruno C (July 2007). "McArdle disease: molecular genetic update". Acta Myologica. 26 (1): 53–7. PMC   2949323 . PMID   17915571.
  17. ↑ Grünfeld JP, Ganeval D, Chanard J, Fardeau M, Dreyfus JC (June 1972). "Acute renal failure in McArdle's disease. Report of two cases". The New England Journal of Medicine. 286 (23): 1237–41. doi:10.1056/NEJM197206082862304. PMID   4502558.
  18. ↑ Burwinkel B, Bakker HD, Herschkovitz E, Moses SW, Shin YS, Kilimann MW (April 1998). "Mutations in the liver glycogen phosphorylase gene (PYGL) underlying glycogenosis type VI". American Journal of Human Genetics. 62 (4): 785–91. doi:10.1086/301790. PMC   1377030 . PMID   9529348.
  19. ↑ Chang S, Rosenberg MJ, Morton H, Francomano CA, Biesecker LG (May 1998). "Identification of a mutation in liver glycogen phosphorylase in glycogen storage disease type VI". Human Molecular Genetics. 7 (5): 865–70. doi: 10.1093/hmg/7.5.865 . PMID   9536091.
  20. ↑ Tang NL, Hui J, Young E, Worthington V, To KF, Cheung KL, et al. (June 2003). "A novel mutation (G233D) in the glycogen phosphorylase gene in a patient with hepatic glycogen storage disease and residual enzyme activity". Molecular Genetics and Metabolism. 79 (2): 142–5. doi:10.1016/S1096-7192(03)00068-4. PMID   12809646.
  21. ↑ Shimada S, Matsuzaki H, Marutsuka T, Shiomori K, Ogawa M (July 2001). "Gastric and intestinal phenotypes of gastric carcinoma with reference to expression of brain (fetal)-type glycogen phosphorylase". Journal of Gastroenterology. 36 (7): 457–64. doi:10.1007/s005350170068. PMID   11480789. S2CID   25602637.
  22. ↑ Alemany S, Pelech S, Brierley CH, Cohen P (April 1986). "The protein phosphatases involved in cellular regulation. Evidence that dephosphorylation of glycogen phosphorylase and glycogen synthase in the glycogen and microsomal fractions of rat liver are catalysed by the same enzyme: protein phosphatase-1". European Journal of Biochemistry. 156 (1): 101–10. doi: 10.1111/j.1432-1033.1986.tb09554.x . PMID   3007140.
  23. ↑ Cori CF, Schmidt G, Cori GT (May 1939). "The Synthesis of a Polysaccharide From Glucose-1-Phosphate in Muscle Extract". Science. 89 (2316): 464–5. Bibcode:1939Sci....89..464C. doi:10.1126/science.89.2316.464. PMID   17731092.
  24. ↑ Cori GT, Cori CF (July 1940). "The kinetics of the enzymatic synthesis of glycogen from glucose-1-phosphate". Journal of Biological Chemistry. 135 (2): 733–756. doi: 10.1016/S0021-9258(18)73136-0 .
  25. ↑ Green AA, Cori GT (July 7, 1943). "Crystalline Muscle Phosphorylase I. Preparation, Properties, and Molecular Weight". Journal of Biological Chemistry. 151: 21–29. doi: 10.1016/S0021-9258(18)72110-8 .
  26. ↑ Cori GT, Green AA (July 1943). "Crystalline muscle phosphorylase II prosthetic group". Journal of Biological Chemistry. 151 (1): 21–29. doi: 10.1016/S0021-9258(18)72113-3 .

Further reading

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