Molecular characteristics of the totally dependent and independent forms of glycogen synthase of rabbit skeletal muscle

Brown, Nathan P.; Larner, Joseph

doi:10.1016/0005-2744(71)90088-x

Cited by 85 publications

(22 citation statements)

References 18 publications

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“…The curious transient effect of sucrose alone on synthetase activity suggests a dual mode of regulation first relative to the supply of sugar and second relative to the presence or absence of auxin, as does the failure of higher sucrose concentrations to duplicate the activating effect of IAA. The dependence upon energy metabolism is compatible with a mechanism of phosphorylative activation and dephosphorylative deactivation of glucan synthetase analogous to known mechanisms of regulation of glycogen phosphorylase and glycogen synthetase (6,39,43,47). To distinguish conclusively among these and other possible activation mechanisms requires experiments at the enzymological level, especially with solubilization of enzyme activity, experiments that are currently in progress.…”

Section: Data Insupporting

confidence: 52%

Regulation of β-Glucan Synthetase Activity by Auxin in Pea Stem Tissue

Ray

1973

Plant Physiol.

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The 2-to 4-fold rise in particle-bound 3-glucan synthetase (uridine diphosphate-glucose:,6-1 ,4-glucan glucosyltransferase) activity that can be induced by indoleacetic acid in pea stem tissue is not prevented by concentrations of actinomycin D or cycloheximide that inhibit growth and macromolecule synthesis. The rise is concluded to be a hormonally induced activation of previously existing, reversibly deactivated enzyme. The activation is not a direct allosteric effect of indoleacetic acid or sugars. It is blocked by inhibitors of energy metabolism, by 2-deoxyglucose, and by high osmolarity, but not by Ca'+ at concentrations that inhibit auxin-induced elongation and prevent promotion of sugar uptake by indoleacetic acid, and not by a, a'-dipyridyl at concentrations that inhibit formation of hydroxyproline. Regulation of the system could be due either to an ATP-dependent activating reaction affecting this enzyme, or to changes in levels of a primer or a lipid cofactor.Under conditions previously defined (37), treatment of pea stem tissue with IAA or other auxins causes a rapid, temperature-dependent rise in the level of particle-bound /8-glucan synthetase activity (UDP-glucose:/8-1 ,4-glucan glucosyltransferase) obtainable from the tissue. This report considers how this hormonal effect depends upon cellular metabolism. A somewhat similar investigation of the effect of IAA, applied in lanolin paste, on GDP-glucose-dependent glucan synthetase activity in stem tissue of whole decapitated pea seedlings was published recently (48). METHODSPlant material and glucan synthetase preparation and assay were as described previously (37). Briefly, pea stem segments 8 mm long cut from the region of maximal elongation rate were kept in a moist atmosphere at 35 C for 2.5 to 3 hr to reduce glucan synthetase activity substantially below the initial level; then a medium containing usually 30 mm sucrose was added and incubation at 35 C was continued for 1 hr. Then the tissue was treated with plus-or minus-IAA media at a specified temperature. In the case of inhibitor experiments the media also contained 16 mm K phosphate buffer, pH 6.1, and 'Supported by a grant from the National Science Foundation. when necessary to ensure establishment of the appropriate inhibition by the time of addition of IAA the sucrose pretreatment media also contained the inhibitor, as specified for the experiments reported. At the end of the treatment period the tissue was chilled on ice, washed with ice water, and used for preparation and assay of glucan synthetase (37).In Vivo Isotope Incorporation Experiments. Samples of 50 segments were incubated in 3.0 ml of labeled substrate in 16 mM K phosphate buffer, pH 6.1, on a reciprocating shaker (120 oscillations/min) at 25 C. At the conclusion of incubation the segments were washed thoroughly with ice water. For assay of incorporation from sugars into particles and cell wall the segments were ground in the same manner (37) as for glucan synthetase assay; the cell wall residue (1,OOOg) and particle pe...

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Section: Data Insupporting

confidence: 52%

Regulation of β-Glucan Synthetase Activity by Auxin in Pea Stem Tissue

Ray

1973

Plant Physiol.

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“…Large errors can arise in this determination when the overall shape of the protein differs greatly from globular, such as the triangular form that these molecules would have if they exhibited an arrangement similar to PaGS. The two studies that report a trimeric oligomerization for rabbit muscle (23) and rat liver GS (24) were performed by sedimentation equilibrium centrifugation, the technique that was used in the present study to determine the molecular mass of PaGS in solution and that does not depend on the shape of the molecule. A much more recent report provides additional indirect evidence that muscle GS can exist as a trimer (25).…”

Section: Resultsmentioning

confidence: 99%

Crystal Structure of an Archaeal Glycogen Synthase

Horcajada

Guinovart

Fita

et al. 2006

Journal of Biological Chemistry

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Glycogen and starch synthases are retaining glycosyltransferases that catalyze the transfer of glucosyl residues to the non-reducing end of a growing ␣-1,4-glucan chain, a central process of the carbon/energy metabolism present in almost all living organisms. The crystal structure of the glycogen synthase from Pyrococcus abyssi, the smallest known member of this family of enzymes, revealed that its subunits possess a fold common to other glycosyltransferases, a pair of ␤/␣/␤ Rossmann fold-type domains with the catalytic site at their interface. Nevertheless, the archaeal enzyme presents an unprecedented homotrimeric molecular arrangement both in solution, as determined by analytical ultracentrifugation, and in the crystal. The C-domains are not involved in intersubunit interactions of the trimeric molecule, thus allowing for movements, likely required for catalysis, across the narrow hinge that connects the Nand C-domains. The radial disposition of the subunits confers on the molecule a distinct triangular shape, clearly visible with negative staining electron microscopy, in which the upper and lower faces present a sharp asymmetry. Comparison of bacterial and eukaryotic glycogen synthases, which use, respectively, ADP or UDP glucose as donor substrates, with the archaeal enzyme, which can utilize both molecules, allowed us to propose the residues that determine glucosyl donor specificity.

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“…Any phosphate present before phosphorylation is not considered. (68,86). The highest specific activity so far obtained for heart synthase was 7.3 (in this thesis) and the preparation used for SDS electrophoresis had a specific activity of 6.6.…”

mentioning

confidence: 89%

“…The first method made use of re peated precipitation with 17% ethajnol as described previously for skeletal muscle enzyme (47,68 Non-radioactive phosphorylase _a was prepared by the procedure described later for preparation of radioactive a.…”

Section: +mentioning

confidence: 99%

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Studies on bovine heart glycogen synthase phosphatase

Nakai

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Molecular characteristics of the totally dependent and independent forms of glycogen synthase of rabbit skeletal muscle

Cited by 85 publications

References 18 publications

Regulation of β-Glucan Synthetase Activity by Auxin in Pea Stem Tissue

Regulation of β-Glucan Synthetase Activity by Auxin in Pea Stem Tissue

Crystal Structure of an Archaeal Glycogen Synthase

Studies on bovine heart glycogen synthase phosphatase

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