Phosphorylase


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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.
Predictive role of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase expression in colorectal cancer patients receiving adjuvant 5-fluorouracil.
It has been suggested that CRC tumours respond to 5-FU when there are low TS, dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) expression levels [6].
The scientists also showed that the enzyme, GDP-L-galactose phosphorylase, has a key role in controlling vitamin C accumulation in response to light.
1 ppm) concentrations of deltamethrin and at the end of the exposure periods, the fish were stunned to death and target organs like gill, liver and muscle were dissected out and glycogen phosphorylase was estimated by method of Sutherland (1955) and glucose-6-phosphatase was estimated by method of Yeung et al,.
Her biopsy revealed multifocal rhabdomyolysis with myofiber necrosis and absence of phosphorylase staining consistent with McArdle disease (type V glycogenosis) (Fig.
Louis, MO) has patented a method for introducing sucrose phosphorylase activity into plants by transformation with a gene for the enzyme increases the rate of sucrose hydrolysis, leading to increased starch, oil, and/protein levels.
Fodosine(TM) is a purine nucleoside phosphorylase (PNP) inhibitor, which functions by blocking the DNA synthesis machinery of the body's T-cells.
We believe PSN357's ability in pre-clinical studies to inhibit glycogen phosphorylase and reduce blood glucose levels may ultimately offer a competitive therapeutic option for diabetes patients.
The study, which evaluated the pharmacokinetic profile for this oral formulation, measured BCX-4208 inhibition of the target enzyme purine nucleoside phosphorylase (PNP), and included detailed safety evaluations of renal and liver function, hematologic parameters, immunological markers, and cardiac function as measured through continuous ECG monitoring, including detailed QTc evaluations.
Metabolic Diseases of Muscles These are caused by inherited chemical deficiencies of a specific enzyme, such as phosphorylase (McArdle's disease), acid maltase (Pompe's disease) or carnitine palmitoyl transferase.
Using deletion analysis and site-directed metagenesis we have identified promoter elements that regulate the glycogen phosphorylase gene during cell differentiation of Dictyostelium," Rutherford reports.