Glycogen synthetase phosphatase

D) inhibition of glycogen synthetase phosphatase activity in liver... 

The less active phosphorylated form of glycogen synthetase is dephos-phorylated, causing the enzyme to become active. Insulin causes activation of the phosphatase that catalyzes this reaction. 

A. After a high-carbohydrate meal, glycogen synthetase is activated by a phosphatase. The ratio of phosphorylase a to phosphorylase b is decreased by a phosphatase, so glycogen degradation decreases. Red blood cells continue to use glucose and form lactate at their normal rate. 

The formulas show the a-carbon and the side chain of the amino acid residues, line phosphatase, phosphorylase kinase, glycogen synthetase, troponin, RNA polymerase, polynucleotide, phosphorylase, and triglyceride lipase. Phosphoserine is also found in nonenzyme proteins which include histones, protamiens, ribosomal proteins, membrane proteins, ovalbumin, casein, and phosvitin often in substantial amounts. For example, there are 119 phosphoserines and only one phosphothreonine residue in phosvitin (72). 

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. 

A phosphatase dephosphorylates glycogen phosphorylase and glycogen synthetase, inactivating and activating them, respectively. The phosphatase becomes active in response to high concentrations of glucose. 

The synthesis of glycogen in rat adipose tissue is catalysed by multiple D-glucose 6-phosphatase-dependent forms of glycogen synthetase. Hormones... 

Fig. 15.3. Pathways of glycogen metabolism. 15.16, Glycogen synthetase (liver) 15.11, brancher enzyme 15.13, phosphorylase (liver) 15.15, phosphorylase kinase (liver) 15.12, phosphorylase (muscle) 15.10, debrancher enzyme (liver + muscle) 15.8, glu-cose-6-phosphatase (liver) 15.8a, glucose-6-phosphate translocase 15.5, fructose-1,6-di-phosphatase 15.9, a-glucosidase UDPGlc, uridine diphosphate glucose Glc-l-P, glucose-1-phosphate Glc-6-P, glucose-6-phosphate F-6-P, fructose-6-phosphate F-l,6-DiP, fructose- 1,6-diphosphate...

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 ... 

Two reports of a new genetic abnormality in primary gout associated with elevated intracellular PP-ribose-P levels and increased PP-ribose-P synthetase have been described in detail at this meeting. The hyperuricemia of glycogen storage disease (Type 1) caused by deficient glucose-6-phosphatase, has been shown by a... 

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