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 ?
Fructose-1,6-bisphosphatase activity was measured by the method of Gancedo and Gancedo (1971), pyruvate kinase activity was estimated by the method of Pogson and Denton (1967), lactate dehydrogenase activity was estimated by the method of King (1965), glycogen synthase activity was estimated by the method of Leloir and Goldemberg (1962), glycogen phosphorylase activity was estimated by the method of Cornblath et al.
The activity of this glycogen phosphorylase enzyme and the content of glycogen were reduced in fructose fed rats.
From the data presented in the table 1, it was noticed that there is significant elevation in the glycogen phosphorylase level in the gill, muscle and liver of fish exposed to lethal and sublethal concentration of deltamethrin.
As the rate of glycogenolysis is regulated by glycogen phosphorylase (GP), inhibition of this key enzyme may constitute a therapeutic option for the treatment of type 2 diabetes.
Ischemia modified albumin, free fatty acids, whole blood choline, B-type natriuretic peptide, glycogen phosphorylase BB, and car diac troponin.
Additionally, N- Trisaccharide increased glycogen synthase and decreased glycogen phosphorylase activity in diabetic rats.
Complete amino acid sequence of rabbit muscle glycogen phosphorylase.
Effect of green tea extract on the levels of glycogen and the activities of glycogen synthase and glycogen phosphorylase in liver
The clinical pipeline will include (OSI) Prosidion's lead compound, PSN9301, a Dipeptidyl Peptidase IV (DPIV) inhibitor currently in Phase II clinical trials, the glycogen phosphorylase inhibitor (PSN357) currently in a Phase I clinical trial and (OSI) Oncology's novel c- kit/KDR inhibitor (OSI-930) which is in Phase I trials.
In addition to PSN9031, (OSI) Prosidion is developing additional product candidates including a glycogen phosphorylase inhibitor currently in a Phase I clinical trial and a glucokinase activator scheduled to enter a Phase I clinical trial in 2006.
He has solved the structures of numerous important proteins, including angiogenin and related ribonucleases, angiotensin-converting enzymes, bacterial toxins and superantigens, eosinophil-granule proteins, galactosyltransferases, Charcot-Leyden crystal protein, ct-Iactalbumin, glycogen phosphorylase, and foot-and-mouth disease virus; the first animal virus structure ever solved outside the United States.