Liver glycogen synthetase

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...

Glycogen metabolism disorders Amylo-l,6-glucosidase defect Liver phosphorylase defect Glycogen synthetase defect... 

Graham, L L, Whistler, R L, Uridine 5 -(5-Thio-a-D-glucopyranosyl pyrophosphate) chemical synthesis and activation of rat liver glycogen synthetase. Biochemistry, 15, 1189-1194, 1976. 

D) phosphorylase, pyruvate kinase, and glycogen synthetase are phosphoiylated in liver... 

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

D. If the phosphodiesterase that degrades cAMP were inhibited, cAMP levels would rise. Protein kinase A would become more active in the liver and muscle, pyruvate kinase would become less active, and glycogen synthetase activity would be decreased. 

An enzyme capable of synthesizing glycogen from uridine 5-(a-D-gluco-pyranosyl pyrophosphate) was first found by Leloir and Cardini in the liver in 1957. Similar enzymes (glycogen synthetases) have since been found in most other mammalian tissues, in some invertebrates, - ... 

A non-phosphorylated form of glycogen phosphorylase B (EC 2.4.1.1) has been isolated from rabbit liver.Co-operative interactions between the substrate-binding sites become more pronounced in the presence of inhibitors, ATP, and D-glucose, and less pronounced in the presence of the activator AMP. Isoenzymes of glycogen phosphorylase and glycogen synthetase are preserved in chick embryo liver and in the liver of adult chicken. The changes which were observed in the ratio between phosphorylases a and b, on the one hand, and glycogen synthetases I and D on the other, do not fit into the Hers scheme for the liver of adult mammals. 

Stage 1. Assembly of Primer. In 1972 Krisman first provided firm evidence to show that a glycoprotein primer was required for the synthesis of glycogen. Subsequently Krisman and Barengo (1975) extended this study and distinguished between a glycogen initiator synthetase and the well-known glycogen synthetase of liver. 

A good illustration of the regulatory properties of cAMP occurs in liver stimulated by glucagon. cAMP activates a protein kinase which phosphorylates both phosphorylase and glycogen synthetase, but while phosphorylase is activated, glycogen synthetase is inhibited by the phosphorylation. Consequently, cAMP at the same time stimulates glycogen breakdown and inhibits glycogen synthesis. 

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