In Vitro Hormonal Regulation of Glycogen Phosphorylase Activity in Fat Body of the Tropical Cockroach, Blaberus discoidalis

1995 ◽  
Vol 98 (3) ◽  
pp. 234-243 ◽  
Author(s):  
Jae H. Park ◽  
Larry L. Keeley
Keyword(s):  
Hormonal Regulation ◽  
Glycogen Phosphorylase ◽  
Fat Body ◽  
Phosphorylase Activity ◽  
Blaberus Discoidalis ◽  
Glycogen Phosphorylase Activity

scholarly journals The effects of calcium ions, ionophore A23187 and inhibition of energy metabolism on protein degradation in the rat diaphragm and epitrochlearis muscles in vitro

1980 ◽  
Vol 190 (3) ◽  
pp. 593-603 ◽  
Author(s):  
P H Sugden
Keyword(s):  
Energy Metabolism ◽  
Protein Degradation ◽  
Glycogen Phosphorylase ◽  
Activity Ratio ◽  
Ionophore A23187 ◽  
Rat Diaphragm ◽  
Phosphorylase Activity ◽  
Glycogen Phosphorylase Activity

1. The effects of external Ca2+, EGTA, ionophore A23187, CN-, dinitrophenol and iodoacetamide on the rate of protein degradation in the rat diaphragm and epitrochlearis muscles in vitro were investigated. 2. External Ca2+ increased protein degradation when compared with external EGTA. Protein degradation was further increased by Ca2+ + ionophore A23187. 3. EGTA and ionophore A23187 decreased ATP and phosphocreatine concentrations and the ATP/ADP ratio. 4. CN-, dinitrophenol and iodoacetamide decreased protein degradation, presumably by interfering with energy metabolism. 5. The effects of EGTA may be caused by disturbances in energy metabolism. The effects of ionophore A23187 cannot be readily explained by disturbances in energy metabolism. 6. Incubation of diaphragms with Ca2+ causes a rapid increase in whole-tissue Ca content. This is further stimulated by ionophore A23187. The uptake of Ca2+ may be, at least in part, into the cytoplasm because an increase in the glycogen phosphorylase activity ratio is observed. 7. A Ca2+-activated proteinase is present in rat heart and diaphragm. This enzyme may mediate in part the effects of Ca2+ described above. The apparent KA of this enzyme for Ca2+ is about 0.25 mM. 8. Because effects of ionophore A23187 cause a large increase in whole-tissue Ca content and because the Ca2+-activated proteinase has a relatively low affinity for Ca2+, it is felt that the effects of Ca2+ upon muscle proteolysis are unlikely to be of importance in steady-state protein turnover in vivo. The mechanism may, however, be important in breakdown of necrotic tissue in the living animal.

scholarly journals Regulation of locust fat-body phosphorylase

1973 ◽  
Vol 135 (1) ◽  
pp. 37-41 ◽  
Author(s):  
S. W. Applebaum ◽  
H. M. Schlesinger
Keyword(s):  
Glycogen Phosphorylase ◽  
Fat Body ◽  
Competitive Inhibitor ◽  
Differential Centrifugation ◽  
Phosphorylase Activity ◽  
Optimum Activity ◽  
Ph Values ◽  
Glycogen Phosphorylase Activity ◽  
Glycogen Particles

1. Glycogen phosphorylase of locust fat-body was partially purified by differential centrifugation and dissociation from glycogen particles at two pH values. 2. Optimum activity was obtained at pH6.6–6.7. 3. The calculated apparent Km values for glycogen and glucose 1-phosphate were 0.08% and 10–13mm respectively. 4. 5′-AMP activated in the range 5μm–1mm. 5. Glucose 6-phosphate is a competitive inhibitor for the substrate glucose 1-phosphate (Ki=1.7mm). 5′-AMP abolishes this inhibition. Glucose weakly inhibits (Ki=25–30mm), but trehalose does not inhibit even at 100mm. 6. It is suggested that glucose 6-phosphate is a major regulator of glycogen phosphorylase activity in locust fat-body.

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