Possibility of metabolite control of liver glycogen synthetase activity

Gold, Alvin H.

doi:10.1021/bi00806a034

Cited by 64 publications

(19 citation statements)

References 14 publications

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“…Thus cAMP stimulates one or more specific protein kinases which transfer phosphate from ATP to phosphorylase b and to synthetase a; this results in activation of the former and inactivation of the latter, which together bring about an acceleration of glycogen breakdown and a reduction of glycogen synthesis. Liver glycogen synthetase (both a and b forms) is stimulated by glucose-6-phosphate and phosphate (MERSMANN and SEGAL, 1967) and is inhibited by ATP and ADP (GOLD, 1970).…”

Section: C) Glycogen Cyclementioning

confidence: 99%

Effects of Catecholamines on Metabolism

Himms‐Hagen¹

1972

Catecholamines

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Section: C) Glycogen Cyclementioning

confidence: 99%

Effects of Catecholamines on Metabolism

Himms‐Hagen¹

1972

Catecholamines

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“…One form is therefore inactive and the other active in vivo, whatever the concentration of glucose-6-phosphate. Other properties of the two forms have been described [12][13][14][15][16]. The phospho-and the dephosphosynthetase have been called respectively D (glucose-6-phosphate dependent) and I (glucose-6-phosphate independent) by Hizukuri and Lamer [14], b (inactive) and a (active) by Mersmann and Segal [13].…”

Section: The Rate Limiting Enzymes; Their Phosphorylation and Dephospmentioning

confidence: 99%

The control of glycogen metabolism in the liver

1970

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“…This concentration of glucose-6-phosphate was capable in vitro of activating the D-form of glycogen synthase to about 50 per cent maximal activity. However, since many intermediates are known to affect glycogen synthase activity, 35 it is unlikely that glucose-6-phosphate alone controls the activity of this enzyme. These results raise questions as to the relative role of glucose-6-phosphate and the relationship of the two forms of glycogen synthase for the physiologic synthesis of glycogen in human fetal liver.…”

Section: Studies In Organ Culturementioning

confidence: 99%

Hormonal Regulation of Glycogen Metabolism in Human Fetal Liver: I. Normal Development and Effects of Dibutyryl Cyclic AMP, Glucagon, and Insulin in Liver Explants

1975

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Glycogen accumulates in human fetal liver beginning at the eighth week of gestation. A parallel increase in total glycogen synthase activity is found, although the I-form activity remains low and constant throughout the first two thirds of gestation. Total phosphorylase activity increases slightly during this period, with the proportion in the active form amounting to about one half of the total throughout. After an initial rapid decline, the glycogen concentration in explants of human fetal liver remained constant for twenty to forty hours at about 20 per cent of the in vivo level. Incubation with glucagon, cyclic AMP (adenosine 3',5'-monophosphate) or its dibutyryl derivative markedly reduced tissue glycogen concentrations while insulin brought about a small increase. The effect of maximal doses of dibutyryl cyclic AMP and glucagon were the same, and the combination of agents produced no further effect. The response to dibutyryl cyclic AMP was apparent by one hour and maximal by three to six hours, whereas the response to insulin required about six hours to be detected, and it continued for at least eighteen hours. Insulin antagonized the glycogenolytic effect of low doses of glucagon or theophylline but was without significant effect in the presence of high glucagon concentrations. Glucagon stimulated cyclic AMP output from explants, and this effect was further augmented by theophylline. Insultin had no consistent effect on cyclic AMP output in either the presence or the absence of glucagon or theophylline. Incubation with dibutyryl cyclic AMP resulted in a decrease of glycogen synthase I-form activity, while insulin tended to increase this enzyme activity. In neither circumstance was the proportion of active phosphorylase altered. These results suggest that the regulation of glycogen levels in human fetal liver by cyclic AMP, glucagon, and insulin may entail alterations in the activity of glycogen synthase activity without necessitating alterations in phosphorylase activity. Cyclic AMP or glucagon was capable of depleting tissue glycogen stores in tissue from fetuses of six weeks' gestation. Insulin increased tissue glycogen concentrations in tissue from fetuses of seven or more weeks.

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Possibility of metabolite control of liver glycogen synthetase activity

Cited by 64 publications

References 14 publications

Effects of Catecholamines on Metabolism

Effects of Catecholamines on Metabolism

The control of glycogen metabolism in the liver

Hormonal Regulation of Glycogen Metabolism in Human Fetal Liver: I. Normal Development and Effects of Dibutyryl Cyclic AMP, Glucagon, and Insulin in Liver Explants

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