phosphorylase


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phosphorylase

 [fos-for´ĭ-lās]
an enzyme that, in the presence of inorganic phosphate, catalyzes the conversion of glycogen into glucose-1-phosphate.

phos·phor·y·lase

(fos-fōr'i-lās),
An enzyme cleaving poly(1,4-α-d-glucosyl)n with orthophosphate to form poly(1,4-α-d-glucosyl)n-1 and α-d-glucose 1-phosphate. The active form of the enzyme is a phosphorylated protein.

phosphorylase

/phos·phor·y·lase/ (fos-for´ĭ-lās)
1. any of a group of enzymes that catalyze the phosphorolysis of glycosides, transferring the cleaved glycosyl group to inorganic phosphate. When not qualified with the substrate name, the term usually denotes glycogen phosphorylase (animals) or starch phosphorylase (plants).
2. any of a group of enzymes that catalyze the transfer of a phosphate group to an organic acceptor.

phosphorylase

(fŏs′fər-ə-lās′, -lāz′)
n.
Any of a class of enzymes that catalyze the attachment of a phosphate group to another molecule.

phosphorylase

[fosfôr′ilās]
Etymology: Gk, phosphoros, bringer of light + ase, enzyme suffix
any of a group of physiologically important enzymes that catalyze reactions between phosphates and glycogen or other starch components, yielding glucose-1-phosphate.

phos·phor·y·lase

(fos-fōr'i-lās)
A phosphorylated enzyme cleaving poly(1,4-α-d-glucosyl)n with inorganic phosphate to form poly(1,4-α- d-glucosyl)n-1 and α-d-glucose 1-phosphate.

muscle enzymes

the table lists some of the most often-mentioned enzymes present in skeletal muscle, with their locations and functions. Apart from actomyosin and myosin ATPases which are associated with the contractile mechanism, they are by no means specific to muscle, being present and highly active also in other tissues. See also Krebs cycle, muscle fibre types.
Table 1: Muscle enzymes
Name SiteCatalyses…
Actomyosin ATPase (amATPase) myosin head groups hydrolysis (Mg-dependent and triggered by rise in [Ca2+]) of terminal phosphate group of ATP when head-group is in interaction with actin, releasing energy that powers force- generation. (Compare myosin ATPase)
Creatine kinase (CK) cytoplasm transfer of phosphate group from creatine phosphate to ADP, producing ATP and creatine. Isoenzymes can be distinguished in blood when either skeletal or cardiac muscle has been damaged.
Hexokinase (HK) cytoplasm 'capture' of glucose after uptake from the blood, by conversion to the impermeant glucose 6-phosphate, in type 1 muscle fibres, which utilize glucose directly.
Lactate dehydrogenase (LDH) cytoplasm reduction of pyruvate to lactate when oxygen tension is low, and the converse when it is high. Isoenzymes can be distinguished in blood when either skeletal or cardiac muscle has been damaged.
Myosin ATPase (mATPase) myosin head groups hydrolysis (Ca2+ dependent, Mg2+ independent) of terminal phosphate group of ATP by head group alone, not interacting with actin (so not contraction-producing: cf actomyosin ATPase). Basic histochemical marker for fast vs. slow fibres.
Phosphofructokinase (PFK) cytoplasm conversion of fructose 6-phosphate to fructose 1,6-diphosphate; rate-limiting for glycolysis, and sensitive to very many stimulatory and inhibitory influences.
Phosphorylase (PPL) cytoplasmremoval of hexose units, one at a time, from glycogen, to form glucose 1-phosphate: rate-limiting enzyme of, and histochemical marker for, glycogenolysis.
Pyruvate dehydrogenase (PDH) mitochondrial envelope oxidative decarboxylation of pyruvate (from cytoplasm) to form acetyl CoA, which thence feeds into tricarboxylic acid (Krebs) cycle
Sarcoplasmic reticulum ATPase (srATPase) SR membrane pumping of [Ca2+] back into SR after its electrically stimulated release
Succinate dehydrogenase (SDH) mitochondrial inner membrane oxidation of succinate to fumarate, in tricarboxylic acid (Krebs) cycle. Histochemical marker for aerobic capacity.

glycogenolysis

removal of a glucose molecule from glycogen, by the action of the enzyme glycogen phosphorylase, present in liver, kidneys, muscle and brain. The products are a glycogen molecule that is one glucose residue shorter than before and glucose-1-phosphate. This in turn is converted to glucose-6-phosphate, from which free glucose can be released from the liver and kidneys (but not from skeletal muscle or brain) by the action of glucose-6-phosphatase. See also glucose, glycolysis.

phosphorylase

a key regulatory enzyme that, in the presence of inorganic phosphate, catalyzes the removal of one glucose unit from glycogen to glucose-1-phosphate.

citrulline phosphorylase
see ornithine carbamoyl transferase.
phosphorylase kinase
an enzyme that activates phosphorylase by catalyzing the phosphorylation of serine. See also kinase.
References in periodicals archive ?
Glycogen phosphorylase isoenzyme BB in diagnosis of myocardial ischaemic injury and infarction.
Interestingly, cones express glycogen phosphorylase (Brennenstuhl et al.
Leklem and Shultz (18) indicate that exercise stimulates the release and activation of the enzyme glycogen phosphorylase pyridoxal phosphate.
Phase II study of Capecitabine with concomitant radiotherapy for patients with locallyadvanced pancreatic cancer: up-regulation of thymidine phosphorylase.
The final product is ATP, which is a form of energy storage needed for cellular metabolism [10-15] This hypothesis would have two consequences on the one hand, degradation of glycogen phosphorylase activation or induction of glycogen as it is explained above, this reaction remained upstream of the cascade of biochemical reactions that lead to a complete glycolysis with the results in the formation of ATP, the other possible entry of glucose into hepatocytes through activation of glycogen synthase.
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.
Furthermore, studies have assessed the seasonality of the glycogen phosphorylase and glycogen synthase enzymes in the green frog (Rana esculenta) liver and have found that phosphorylase is more active during wintertime, while the synthase, during the summer, suggesting a seasonal influence on the activity of these enzymes (SCAPIN; DI GIUSEPPE, 1994).
Glycogen phosphorylase is the primary enzyme involved in this breakdown and Aegle marmelos appears to inhibit glycogen phosphorylase, thereby regulating the glycogenolysis pathway and leading to a decrease in the glucose level in the blood (Narendhirakannan et al.
Expression of glycogen phosphorylase, responsible for glycogen catabolism was increased 4-fold by P4 when compared to controls (P<0.
Galactosaemia, in fact, often results in hypoglycaemia caused by hepatic accumulation of galactose-1phosphate, which inhibits enzymes of glycogenolysis; including glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, phosphoglucomutase and glycogen phosphorylase.
The study in Cell outlined a new role for a protein called polynucleotide phosphorylase (PNPASE) in regulating the import of RNA into mitochondria.