scholarly journals Glycogen phosphorylase: A multifaceted enzyme

1989 ◽  
Vol 54 (6) ◽  
pp. 203-229 ◽  
Author(s):  
Louise N. Johnson
Keyword(s):  
Glycogen Phosphorylase

Immunocytochemical detection of hepatic carbohydrate metabolic enzymes: Improved resolution with polyethylene glycol embedding and visio-bond semithin sections

1992 ◽  
Vol 50 (1) ◽  
pp. 792-793
Author(s):  
Kuixiong Gao ◽  
Randal E. Morris ◽  
Bruce F. Giffin ◽  
Robert R. Cardell
Keyword(s):  
Polyethylene Glycol ◽  
Glycogen Phosphorylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthase ◽  
Metabolic Enzymes ◽  
Silver Stain ◽  
Accurate Localization ◽  
Immunocytochemical Detection ◽  
Semithin Sections ◽  
Parenchymal Cells

Several enzymes are involved in the regulation of anabolic and catabolic pathways of carbohydrate metabolism in liver parenchymal cells. The lobular distribution of glycogen synthase (GS), phosphoenolpyruvate carboxykinase (PEPCK) and glycogen phosphorylase (GP) was studied by immunocytochemistry using cryosections of normal fed and fasted rat liver. Since sections of tissue embedded in polyethylene glycol (PEG) show good morphological preservation and increased detectability for immunocytochemical localization of antigenic sites, and semithin sections of Visio-Bond (VB) embedded tissue provide higher resolution of cellular structure, we applied these techniques and immunogold-silver stain (IGSS) for a more accurate localization of hepatic carbohydrate metabolic enzymes.

Pentacyclic triterpenes, inhibitors of glycogen phosphorylase, as potential drugs for type 2 diabetes: X-ray crystallographic studies

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
SE Zographos ◽  
DD Leonidas ◽  
KM Alexacou ◽  
T Gimisis ◽  
JM Hayes ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Glycogen Phosphorylase ◽  
X Ray ◽  
Pentacyclic Triterpenes

Phytogenic Polyphenols as Glycogen Phosphorylase Inhibitors: The Potential of Triterpenes and Flavonoids for Glycaemic Control in Type 2 Diabetes

2017 ◽  
Vol 24 (4) ◽  
pp. 384-403 ◽  
Author(s):  
Demetres Leonidas ◽  
Joseph Hayes ◽  
Atsushi Kato ◽  
Vassiliki Skamnaki ◽  
Demetra Chatzileontiadou ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Glycaemic Control ◽  
Glycogen Phosphorylase ◽  
Glycogen Phosphorylase Inhibitors

Computation as a Tool for Glycogen Phosphorylase Inhibitor Design

2010 ◽  
Vol 10 (12) ◽  
pp. 1156-1174 ◽  
Author(s):  
Joseph M. Hayes ◽  
Demetres D. Leonidas
Keyword(s):  
Glycogen Phosphorylase ◽  
Inhibitor Design ◽  
Glycogen Phosphorylase Inhibitor

Glycogen Phosphorylase in the Fat Body of Two Cockroach Species, Periplaneta americana and Nauphoeta cinerea: Isolation, Partial Characterization of Three Forms and Activation by Hypertrehalosaemic Hormones

1991 ◽  
Vol 46 (1-2) ◽  
pp. 149-162 ◽  
Author(s):  
Gerd Gäde
Keyword(s):  
Anion Exchange ◽  
Glycogen Phosphorylase ◽  
Periplaneta Americana ◽  
Fat Body ◽  
Phosphorylase Kinase ◽  
Phosphorylase Activity ◽  
Strong Inhibitor ◽  
Nauphoeta Cinerea ◽  
Crude Extracts ◽  
Fat Bodies

The presence of endogenous phosphorylase kinase and phosphorylase phosphatase in crude extracts of fat bodies from the cockroaches Nauphoeta cinerea and Periplaneta americana is demonstrated in vitro by activation/inactivation of glycogen phosphorylase under appropriate conditions. Fractionation of fat body extracts of both cockroach species on an anion-exchange medium results in the elution of three peaks with phosphorylase activity. According to their AMP dependency these activity peaks are designated as phosphorylase b (inactive without AMP), phosphorylase ab (active without AMP, but several stimulated with AMP) and phosphorylase a (active without AMP). It is shown chromatographically that incubating crude extracts of fat bodies from both cockroaches, under conditions where the phosphorylase kinase is active, results in all phosphorylase b being converted to the ab- or a-form , whereas under conditions where the phosphorylase phosphatase is active all phophorylase a is converted to the ab- or b-form . Endogenous phosphorylase kinase of N. cinerea crude fat body extract can convert vertebrate phosphorylase b into the a-form , and, conversely, vertebrate muscle p hosphorylase kinase and phosphorylase phosphatase, respectively, are able to convert partially purified N. cinerea phosphorylase aborb and the ab- und a-form , respectively. In resting cockroaches most of the phosphorylase activity resides in the b-form and only a small fraction (10% ) in the a-form , whereas between 26% (N . cinerea) and 35% (P. americana) occurs in the ab-form . Injection of endogenous hypertrehalosaemic peptides into N. cinerea (the decapeptide Bld-HrTH ) or P. americana (the two octapeptides Pea-CAH -I and II) causes interconversion of phosphorylase; after injection, mainly (60% ) phosphorylase a is present, while 25% and 15% exists in the ab- und b-form , respectively. Purification of the three phosphorylase forms from N. cinerea is achieved by anion-exchange chromatography on DEAE-Sephacel followed by affinity chromatography on AMP-Sepharose. The final specific activities are 2.1, 6.9 and 27.2 U /mg protein for the a-, ab- und b-form . The molecular mass of the active molecules on gel filtration is between 173,000 and 177,000, and SDS gel electrophoresis reveals a subunit mass of 87,100, suggesting a homodimeric structure for all three form s. Kinetic studies show hyperbolic saturation curves for the substrates glycogen and Pi respectively, with Kᴍ-values of 0.021, 0.019 and 0.073% for glycogen and 8.3, 6.3 and 17.9 mᴍ for Pi (a-, ab- and b-form ). Phosphorylase a exhibits a more or less hyperbolic response to AMP and needs 70 |iM A M P for m axim al stim ulation. The kinetics for the ab- and b-form s are sigm oidal and maximal activities are displayed at about 3 mᴍ (half-maximum activation as calculated from Hill plots are 55 and 280 μᴍ for the ab- und b-form , respectively). Caffeine is a strong inhibitor of the b-form , but has only a slight inhibiting effect (10 -20 % ) on the ab- and a-form in the presence of AMP.

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