Phosphorylase

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Related to Glycogen phosphorylase: glycogen synthase

phosphorylase

[fäs′fȯr·ə‚lās]
(biochemistry)
An enzyme that catalyzes the formation of glucose-1-phosphate (Cori ester) from glycogen and inorganic phosphate; it is widely distributed in animals, plants, and microorganisms.

Phosphorylase

 

any of a group of transferase enzymes that catalyze the reversible reactions for the transfer of glycosyl groups (monosaccharide residues) to orthophosphate (phosphorolysis). The phosphorylase-catalyzed reaction may be expressed as follows:

where G is a glycosyl group, A is a glycosyl group acceptor, and O is orthophosphate. Seven enzymes are known that transfer hexose groups (from polysaccharides and disaccharides), and eight are known that transfer pentosyl groups (from nucleosides). These enzymes have a high degree of specificity relative to the glycosyl group; such specificity is not always observed, however, in the case of the acceptor.

Phosphorylases are widespread in nature, occurring in protozoans and in the tissues of animals and plants. They play an important role in organisms, catalyzing key reactions of metabolism related to the use of stored carbohydrates and, thus, to the supply of energy to cells. The study of phosphorylases has contributed to advances in enzymology. Phosphorylase-catalyzed reactions provided the model for research on macromolecular synthesis, the binding of an enzyme with a substrate, the allosteric regulation of enzyme activity, the dissociation of enzymes into subunits, and the catalytic conversion of an enzyme from an inactive form into an active form. The most thoroughly studied phosphorylases are those that catalyze the breakdown of gylcogen and starch, which are storage forms of carbohydrates.

V. V. ZUEVSKII

References in periodicals archive ?
Utilization of glycogen phosphorylase BB measurement in the diagnosis of acute coronary syndromes in the event of chest pain.
Activities of glycogen phosphorylase a (A), phosphofructokinase (B), pyruvate kinase (C) and hexokinase determined in postmortem muscles.
C) Explants from the different experimental conditions were labeled with antibodies against glycogen phosphorylase as a marker of cone photoreceptors.
Identification of glycogen phosphorylase and creatine kinase as calpain substrates in skeletal muscle.
Activity of glycogen phosphorylase (GP) and the content of glycogen in cytosolic fraction and the activities of isocitrate dehydrogenase (ICDH) and succinate dehydrogenase (SDH) in mitochondria liver and skeletal muscle of experimental animals Parameters CON FRU GP (A): Liver 4.
Glycogen phosphorylase is an enzyme that exists in two forms, one activated with adenosine mono phosphate (AMP) and the other activated without it, which are interconversible by phosphorylation and dephosphorylation mechanism (Cori and Cori 1945; Cori et al.
Early release of glycogen phosphorylase in patients with unstable angina and transient ST-T alterations.
In one project, the researchers use the cellular enzyme glycogen phosphorylase -- which normally liberates glucose units from huge, energy-storing starch molecules called glycogen when the cell needs more fuel--to run the reaction in reverse using a laboratory-made glucose derivative.
Using their proprietary, systems biology engine for the analysis of genome-scale expression data, and animal models accepted to be good indicators for neuropathic pain in patients, Aestus identified ATx09-002, a glycogen phosphorylase inhibitor, as a potential therapeutic for the treatment of neuropathic pain.
The altered activities of the key enzymes of carbohydrate metabolism such as hexokinase, pyruvate kinase, lactate dehydrogenase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, glucose-6-phosphate dehydrogenase, glycogen synthase and glycogen phosphorylase in liver of diabetic rats were significantly reverted to near normal levels by the administration of tangeretin.
3] conjugated to glycogen phosphorylase b (GPb) from rabbit muscle.
Glycogen phosphorylase activity was measured at 25 [degrees] C in extracts from gemmules according to a modification of the method of Mendicino et al.