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 ?
Furthermore, the present research showed that IOF of 12 mg CrPyr/egg had no effect on glycogen synthase mRNA expression as well as the expression of glycogen phosphorylase mRNA in broiler muscle, which further proved that glucose uptake in the muscle is not synthesized as glycogen stored in muscles.
Targeting tumors that lack methylthioadenosine phosphorylase (MTAP) activity.
Inhibiting glycogen phosphorylase with clove can help block excess glucose release into the bloodstream.
No differences in glycogen synthase (p = 0.9), glycogen phosphorylase (p = 0.9), and glycogen-6-phosphatase (p = 0.7) were apparent between experimental groups (Figures 4(b)-4(d)).
Glycogen phosphorylase (GP) is bound to glycogen in sarcoplasmic reticulum and catalyzes the first step of glycogenolysis after activation, which involves the separation of glucose-1-phosphate from glycogen.
The glycogen phosphorylase gene was expressed in the non-diapause eggs, whereas that in the diapause eggs was highly expressed in the early stage and then downregulated in the late stage.
Des composantes de la societe civile, a Gabes, ont organise, lundi 20 mars 2017, une marche pacifique partant de la Place des martyrs, en direction de Chott Essalem, pour protester contre la degradation de l'environnement par les rejets de phosphorylase en mer.
It is well documented that T cell proliferation and activation is dependent on the purine nucleotide phosphorylase (PNP) enzyme activity.