The role of pyridoxal 5'-phosphate in glycogen phosphorylase catalysis

Biochemistry ◽  
1990 ◽  
Vol 29 (5) ◽  
pp. 1099-1107 ◽  
Author(s):  
Dieter Palm ◽  
Helmut W. Klein ◽  
Reinhard Schinzel ◽  
Manfred Buehner ◽  
Ernst J. M. Helmreich
Keyword(s):  
Glycogen Phosphorylase

scholarly journals Heterologous desensitization of the cyclic AMP-independent glycogenolytic response in rat liver cells

1981 ◽  
Vol 200 (3) ◽  
pp. 509-514 ◽  
Author(s):  
B Bréant ◽  
S Keppens ◽  
H De Wulf
Keyword(s):  
Cyclic Amp ◽  
Glycogen Phosphorylase ◽  
Liver Glycogen ◽  
Receptor Interaction ◽  
Alpha Adrenergic Receptors ◽  
Rat Liver Cells ◽  
Heterologous Desensitization ◽  
Highly Correlated ◽  
Alpha Agonist

Vasopressin and alpha-adrenergic agonists are known to be potent cyclic AMP-independent Ca2+-dependent activators of liver glycogen phosphorylase. When hepatocytes are pre-incubated with increasing concentrations of vasopressin or of the alpha-agonist phenylephrine, they become progressively unresponsive to a second addition of the respective agonist. The relative abilities of six vasopressin analogues and of five alpha-agonists to activate glycogen phosphorylase and to cause subsequent desensitization are highly correlated, indicating that the same vasopressin and alpha-adrenergic receptors are involved in both responses. About 5-times-higher peptide concentrations are needed to desensitize the cells than to activate their glycogen phosphorylase, whereas the concentrations of alpha-agonists required for the desensitization are only twice those needed for the activation of phosphorylase. The desensitization is not mediated by a perturbation in the agonist-receptor interaction. It is clearly heterologous, i.e. it is not agonist-specific, and must therefore involve a mechanism common to both series of agonists. The evidence for a role of Ca2+ movements or phosphatidylinositol turnover is briefly discussed.

scholarly journals Glycogen Phosphorylase in Acanthamoeba spp.: Determining the Role of the Enzyme during the Encystment Process Using RNA Interference

2008 ◽  
Vol 7 (3) ◽  
pp. 509-517 ◽  
Author(s):  
Jacob Lorenzo-Morales ◽  
Jarmila Kliescikova ◽  
Enrique Martinez-Carretero ◽  
Luis Miguel De Pablos ◽  
Bronislava Profotova ◽  
...  
Keyword(s):  
Rna Interference ◽  
Cyst Wall ◽  
Glycogen Phosphorylase ◽  
Catalytic Domain ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Main Tool ◽  
Lower Eukaryotes ◽  
Free Glucose

ABSTRACT Acanthamoeba infections are difficult to treat due to often late diagnosis and the lack of effective and specific therapeutic agents. The most important reason for unsuccessful therapy seems to be the existence of a double-wall cyst stage that is highly resistant to the available treatments, causing reinfections. The major components of the Acanthamoeba cyst wall are acid-resistant proteins and cellulose. The latter has been reported to be the major component of the inner cyst wall. It has been demonstrated previously that glycogen is the main source of free glucose for the synthesis of cellulose in Acanthamoeba, partly as glycogen levels fall during the encystment process. In other lower eukaryotes (e.g., Dictyostelium discoideum), glycogen phosphorylase has been reported to be the main tool used for glycogen breakdown in order to maintain the free glucose levels during the encystment process. Therefore, it was hypothesized that the regulation of the key processes involved in the Acanthamoeba encystment may be similar to the previously reported regulation mechanisms in other lower eukaryotes. The catalytic domain of the glycogen phosphorylase was silenced using RNA interference methods, and the effect of this phenomenon was assessed by light and electron microscopy analyses, calcofluor staining, expression zymogram assays, and Northern and Western blot analyses of both small interfering RNA-treated and control cells. The present report establishes the role of glycogen phosphorylase during the encystment process of Acanthamoeba. Moreover, the obtained results demonstrate that the enzyme is required for cyst wall assembly, mainly for the formation of the cell wall inner layer.

scholarly journals The influence of vasopressin and related peptides on glycogen phosphorylase activity and phosphatidylinositol metabolism in hepatocytes

1979 ◽  
Vol 178 (2) ◽  
pp. 493-496 ◽  
Author(s):  
C J Kirk ◽  
L M Rodrigues ◽  
D A Hems
Keyword(s):  
Glycogen Phosphorylase ◽  
Hepatic Glycogen ◽  
Vasopressin Receptor ◽  
Phosphorylase Activity ◽  
Phosphatidylinositol Metabolism ◽  
Molecular Specificity ◽  
The Individual ◽  
Glycogen Phosphorylase Activity ◽  
Phosphate Incorporation

The relative abilities of seven vasopressin-like peptides to activate hepatic glycogen phosphorylase and stimulate phosphate incorporation into phosphatidylinositol were compared. Although the individual peptides differed in their potencies, the concentrations required to stimulate phosphatidylinositol metabolism were always greater (about 10 times) than those needed to activate phosphorylase. The molecular specificity of the hepatic vasopressin receptor and the role of vasopressin-stimulated phosphatidylinositol turnover are discussed.

Expression of the muscle glycogen phosphorylase gene in patients with McArdle disease: the role of nonsense-mediated mRNA decay

2008 ◽  
Vol 29 (2) ◽  
pp. 277-283 ◽  
Author(s):  
Gisela Nogales-Gadea ◽  
Juan Carlos Rubio ◽  
Israel Fernandez-Cadenas ◽  
Ines Garcia-Consuegra ◽  
Alejandro Lucia ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Glycogen Phosphorylase ◽  
Mrna Decay ◽  
Mcardle Disease ◽  
Nonsense Mediated Mrna Decay
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