Studies on the Allosteric Properties of Glycogen Synthase I

Sølling, Henrik

doi:10.1111/j.1432-1033.1979.tb12890.x

Cited by 28 publications

(28 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As in the purified system (7), high ionic strength also inhibited the phosphorylation reaction. High ionic strength also interferes with the active site (13). ADP and Pi inhibited the rate of phosphorylation, as expected.…”

Section: Effectors On the Synthase 1 Deactivationmentioning

confidence: 52%

Phosphorylation of glycogen synthase in a homogenate of human polymorphonuclear leukocytes

Juhl

Esmann

1981

Mol Cell Biochem

View full text Add to dashboard Cite

Glycogen synthase I in a homogenate of human polymorphonuclear leukocytes was phosphorylated under imitated physiological conditions utilizing the endogenous protein kinases. At subsequent steps of phosphorylation the 32P-labelled synthase was purified and characterized. Limited tryptic hydrolysis of the 32P-labelled synthase released four phosphopeptides (t-A, t-B, t-C, t-D) and subsequent chymotrypsinization of the trypsin resistant core released three phosphopeptides (c-A, c-B, c-C). One Pi/subunit was incorporated within 8-10 min and 2.2 Pi/subunit within 60 min increasing the Kc for Glc-6-P to 4-6 mM. The initial phosphorylation up to 0.8 Pi/subunit occurred mainly in peptide c-A and a linear relation between ratio of independence (RI) of glycogen synthase in the interval RI 0.85 to RI 0.05 and phosphorylation of this peptide of 0.5 Pi was observed. Phosphorylation of this peptide is responsible for the decrease in ratio of independence. From experiments with inhibitors and activators, the initial phosphorylation was found predominantly catalysed by the endogenous cAMP independent synthase kinase, however, the endogenous cAMP dependent protein kinase and phosphorylase kinase also phosphorylate endogenous glycogen synthase I to a minor degree. Circumstantial evidence for a Ca-dependent synthase kinase different from phosphorylase kinase is presented. The endogenous Glc-6-P dependent glycogen synthase occurring in a homogenate of leukocytes disrupted in the presence of NaF incorporated 1.07 Pi/subunit and Kc for Glc-6 was increased from 6-8 mM to 20 mM. From the present and previous experiments [7] a total of 8 major phosphorylatable sites have been defined, one on each of the peptides t-A, t-B, c-B, c-C and two on peptide c-A, which in addition may contain a third site for phosphorylase kinase. Assuming identical subunits, only 13 out of 32 sites are thus covalently modified at maximum phosphorylation. The operational defined synthase R (Kc for Glc-6-P 0.5 mM) and D (Kc for Glc-6-P 2-8 mM) activities correspond to synthase with about 0.8 Pi and 1.8-2.3 Pi/subunit, respectively.

show abstract

Section: Effectors On the Synthase 1 Deactivationmentioning

confidence: 52%

Phosphorylation of glycogen synthase in a homogenate of human polymorphonuclear leukocytes

Juhl

Esmann

1981

Mol Cell Biochem

View full text Add to dashboard Cite

show abstract

“…Since an adjustment to the weights does not guarantee a decrease in the weighted sum of squares and might even result in an increase, the stop criterion for this iterative process may not involve the comparison of weighted sums of squares between iterations; convergence of optimized parameter values is instead used as a stop criterion. Moreover, if the weights are not constructed to be dimensionless as in eqn (12), the dimensions of the weighted sums of squares will depend on the value of (σ 0 /σ 2 ) 2 and may not be compared [28].…”

Section: Algorithm and Weight Estimationmentioning

confidence: 99%

“…G6P (Glc 6-phosphate), which is able to activate even the most extensively phosphorylated GS, is widely considered the most important allosteric modifier, but GS is also inhibited by several other modifiers such as ATP and ADP. It has been shown that G6P is unable to completely reverse inhibition by ATP [11,12].…”

Section: Introductionmentioning

confidence: 99%

Incorporating covalent and allosteric effects into rate equations: the case of muscle glycogen synthase

Palm

Rohwer

Hofmeyr

2014

Biochemical Journal

View full text Add to dashboard Cite

Several enzymes have been described that undergo both allosteric and covalent regulation, but, to date, there exists no succinct kinetic description that is able to account for both of these mechanisms of regulation. Muscle glycogen synthase, an enzyme implicated in the pathogenesis of several metabolic diseases, is activated by glucose 6-phosphate and inhibited by ATP and phosphorylation at multiple sites. A kinetic description of glycogen synthase could provide insight into the relative importance of these modifiers. In the present study we show, using non-linear parameter optimization with robust weight estimation, that a Monod-Wyman-Changeux model in which phosphorylation favours the inactive T conformation provides a satisfactory description of muscle glycogen synthase kinetics. The best-fit model suggests that glucose 6-phosphate and ATP compete for the same allosteric site, but that ATP also competes with the substrate UDP-glucose for the active site. The novelty of our approach lies in treating covalent modification as equivalent to allosteric modification. Using the obtained rate equation, the relationship between enzyme activity and phosphorylation state is explored and shown to agree with experimental results. The methodology we propose could also be applied to other enzymes that undergo both allosteric and covalent modification.

show abstract

“…Both of them use ADP-Glc as a glucosyl donor and have molecular masses of 48 -55 kDa, whereas the yeast and mammalian glycogen synthases have molecular masses of 70 -85 kDa and prefer UDP-glucose. Another feature that differentiates the latter enzymes from bacterial and plant glycogen/starch synthases is their regulation by phosphorylation and allosteric activation by glucose 6-phosphate (7,8). Malfunction of human glycogen synthase has been associated with several metabolic diseases, such as diabetes mellitus and glycogen storage disease (9, 10).…”

mentioning

confidence: 99%

Identification and Characterization of a Critical Region in the Glycogen Synthase from Escherichia coli

Yep

Ballícora

Sivak

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

The cysteine-specific reagent 5,5-dithiobis(2-nitrobenzoic acid) inactivates the Escherichia coli glycogen synthase (Holmes, E., and Preiss, J. Escherichia coli glycogen synthase (EC 2.4.1.21) catalyzes the transfer of a glucosyl unit from ADP-glucose (ADP-Glc) 1 to the non-reducing end of glycogen.ADP-Glcϩ␣1,4-glucan 3 ␣1,4-glucosyl-␣1,4-glucanϩADP (Eq. 1)The reaction was described in bacteria in 1964 (1) and its equilibrium is strongly shifted toward the formation of ADP (2). The glycogen synthase from E. coli has been purified to homogeneity (2), and some of its properties have been characterized (3-6). Bacterial glycogen synthases and plant starch synthases catalyze the same chemical reaction and share between 30 and 36% identity, suggesting that they could have a common structure and catalytic mechanism. Both of them use ADP-Glc as a glucosyl donor and have molecular masses of 48 -55 kDa, whereas the yeast and mammalian glycogen synthases have molecular masses of 70 -85 kDa and prefer UDP-glucose. Another feature that differentiates the latter enzymes from bacterial and plant glycogen/starch synthases is their regulation by phosphorylation and allosteric activation by glucose 6-phosphate (7,8). Malfunction of human glycogen synthase has been associated with several metabolic diseases, such as diabetes mellitus and glycogen storage disease (9, 10). Although there is no obvious sequence similarity between bacterial and mammalian glycogen synthases, it has been proposed that they share a common structure and catalytic mechanism. This was based on prediction of the secondary structure, threading, and hydrophobic cluster analysis (11,12). Despite the importance of these enzymes, little is known about the structure of the catalytic site. More knowledge of the structure-function relationship in bacterial glycogen synthases could be instrumental in understanding the molecular basis of those disorders.Few studies have been made to elucidate possible substratebinding residues, in both bacterial glycogen synthases and plant starch synthases, but the nature of the substrate-binding site remains unclear. Furukawa et al. (13) showed that ADPGlc protects Lys 15 in the E. coli glycogen synthase from reaction with pyridoxal phosphate. Replacement of Lys 15 by Arg, Gln, or Glu, increases the S 0.5 7-, 32-, and 46-fold, respectively (13). In the starch synthase IIa from maize endosperm, Argspecific modification experiments were performed with phenylglyoxal (14). However, the studied Arg residues are not 100% conserved, and, when mutated, no significant shifts in S 0.5 for ADP-Glc were shown. It has been shown that cysteine-reactive reagents inactivate E. coli glycogen synthase, and that this effect could be prevented by the substrates (15). However, the residues in E. coli glycogen synthase that are involved in this inactivation have not been identified. DTNB (5,5Ј-dithiobis(2-nitrobenzoic acid)) has the ability to form mixed disulfide bridges with cysteines, and it has been used to identify the ones involved in catalysis or...

show abstract

Studies on the Allosteric Properties of Glycogen Synthase I

Cited by 28 publications

References 42 publications

Phosphorylation of glycogen synthase in a homogenate of human polymorphonuclear leukocytes

Phosphorylation of glycogen synthase in a homogenate of human polymorphonuclear leukocytes

Incorporating covalent and allosteric effects into rate equations: the case of muscle glycogen synthase

Identification and Characterization of a Critical Region in the Glycogen Synthase from Escherichia coli

Contact Info

Product

Resources

About