Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Glycogen synthetase regulation

Studies by Lamer and coworkers showed that 3 5 -cyclic AMP is an important factor that regulates the interconversion of the two forms of glycogen synthetase. The conversion of the independent into the dependent form is catalyzed by a kinase requiring ATP and Mg +, the activity of which is increased by cyclic AMP. Huijing and Lamer and others showed that muscle kinase appears to be similar to, but not identical with, phosphorylase b kinase, - and that the two enzymes seem to be equally sensitive to stimulation by cyclic AMP. It has been suggested - that cyclic AMP may in this instance act by increasing the affinity of an allosteric site for magnesium on the kinases. As epinephrine and other hormones increase the level of... [Pg.378]

The dependent form can be reconverted into the independent form through dephosphorylation by a specific phosphatase that is inhibited by glycogen this can provide a mechanism for the feedback regulation of glycogen levels in tissues, through the inhibition of reactivation of glycogen synthetase by its own product. [Pg.379]

The independent form can be converted into the dependent form by a difiFerent mechanism. It has been found that addition of calcium ions to certain glycogen synthetase preparations produces a conversion of the independent into the dependent form. This conversion does not involve ATP, and is not aflFected by adenosine 3 5 -cyclic phosphate it requires a protein similar to that involved in the activation of inactive phosphorylase b kinase by Ca ". Thus, calcium appears to exert an effect on the regulation of glycogen synthetase, and it is hypothesized that the inactivation of muscle glycogen synthetase after muscle contraction may be caused by this mechanism, mediated by an alteration of intracellular levels of Ca +. [Pg.379]

Similarly, a complex sequence of steps leads to the synthesis of glycogen (see metabolic regulation, Chapter 16). A protein kinase transforms active glycogen synthetase (I form) into an inactive phosphory-lated form (D form). There are also inactive and active forms of the protein kinase the conversion to the active enzyme is cAMP dependent. It is believed that insulin reduces the level of cAMP and thereby inhibits the protein kinase and the glycogen synthetase [200]. [Pg.531]

Figure 10.6 Hormonal regulation of glycogen synthetase and glycogen phosphorylase — responses to glucagon or adrenaline and insulin. Figure 10.6 Hormonal regulation of glycogen synthetase and glycogen phosphorylase — responses to glucagon or adrenaline and insulin.
There are many examples, including glycogen phosphorylase, glycogen synthetase, pyruvate dehydrogenase (35), and the diflFerence from a classical interaction is that regulator X interacts with an interconverting enzyme (Ep) instead of the pathway enzyme (a or b). [Pg.71]

M. J. Ernest, K. H. Kim, Regulation of rat liver glycogen synthetase D. Rote of glucose 6-phosphate and enzyme sulfhydryl groups in activity and glycogen binding J. Biol. Chem. 249 1974,5011-8. [Pg.1476]

Covalent interconversion of enzymes is well established as a fundamental theme in metabolic regulation. The prototypic reversible interconverting systems include the sequence of phosphorylation/dephosphorylation steps in the activation of mammalian glycogen phosphorylase and pyruvate dehydrogenase as well as the nucleotidyla-tion/denucleotidylation using UTP and ATP in the bacterial glutamine synthetase cascade (see Fig. 1.). [Pg.235]

Enzyme activity can be regulated by covalent modification or by noncovalent (allosteric) modification. A few enzymes can undergo both forms of modification (e.g., glycogen phosphorylase and glutamine synthetase). Some covalent chemical modifications are phosphorylation and dephosphorylation, acetylation and deacetylation, adeny-lylation and deadenylylation, uridylylation and deuridyly-lation, and methylation and demethylation. In mammalian systems, phosphorylation and dephosphorylation are most commonly used as means of metabolic control. Phosphorylation is catalyzed by protein kinases and occurs at specific seryl (or threonyl) residues and occasionally at tyrosyl residues these amino acid residues are not usually part of the catalytic site of the enzyme. Dephosphorylation is accomplished by phosphoprotein phosphatases ... [Pg.110]


See other pages where Glycogen synthetase regulation is mentioned: [Pg.275]    [Pg.197]    [Pg.205]    [Pg.349]    [Pg.377]    [Pg.1347]    [Pg.231]    [Pg.343]    [Pg.344]    [Pg.226]    [Pg.195]    [Pg.92]    [Pg.142]    [Pg.21]    [Pg.530]    [Pg.545]    [Pg.429]    [Pg.163]    [Pg.155]    [Pg.354]    [Pg.597]    [Pg.1012]    [Pg.700]    [Pg.353]   
See also in sourсe #XX -- [ Pg.441 ]

See also in sourсe #XX -- [ Pg.441 ]




SEARCH



Glycogen regulation

© 2024 chempedia.info