Phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor.

A-B + P A + P-B

They include allosteric

Allosteric regulation

In biochemistry, allosteric regulation is the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site . Effectors that enhance the protein's activity are referred to as allosteric activators, whereas those that decrease the protein's activity are...

 enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s that catalyze

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 the production of glucose-1-phosphate

Glucose-1-phosphate

Glucose 1-phosphate is a glucose molecule with a phosphate group on the 1'-carbon.-Catabolic:In glycogenolysis, it is the direct product of the reaction in which glycogen phosphorylase cleaves off a molecule of glucose from a greater glycogen structure.To be utilized in cellular catabolism it must...

 from a glucan

Glucan

A glucan molecule is a polysaccharide of D-glucose monomers linked by glycosidic bonds.Many beta-glucans are medically important.-Types:The following are glucans:-Alpha:...

 such as glycogen

Glycogen

Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

, starch

Starch

Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 or maltodextrin

Maltodextrin

Maltodextrin is a polysaccharide that is used as a food additive. It is produced from starch by partial hydrolysis and is usually found as a creamy-white hygroscopic spraydried powder. Maltodextrin is easily digestible, being absorbed as rapidly as glucose, and might be either moderately sweet or...

. Phosphorylase is also a common name used for glycogen phosphorylase

Glycogen phosphorylase

Glycogen phosphorylase is one of the phosphorylase enzymes . Glycogen phosphorylase catalyzes the rate-limiting step in the degradation of glycogen in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond...

 in honor of Earl W. Sutherland Jr. who in the late 1930's discovered the first phosphorylase.

Function

In more general terms, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor, not to be confused with a phosphatase

Phosphatase

A phosphatase is an enzyme that removes a phosphate group from its substrate by hydrolysing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group . This action is directly opposite to that of phosphorylases and kinases, which attach phosphate groups to their...

 (a hydrolase

Hydrolase

In biochemistry, a hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. For example, an enzyme that catalyzed the following reaction is a hydrolase:-Nomenclature:...

) or a kinase

Kinase

In chemistry and biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, a process referred to as phosphorylation. Kinases are part of the larger family of phosphotransferases...

 (a phosphotransferase). A phosphatase removes a phosphonate group from a donor using water, whereas a kinase transfers a phosphonate group from a donor (usually ATP) to an acceptor.

Enzyme name	Enzymes class	Reaction	Notes
Phosphorylase	Transferase (EC 2.4 and EC 2.7.7)	A-B + H-OP A-OP + H-B	transfer group = A = glycosyl Glycosyl A glycosyl group is a univalent free radical or substituent structure obtained by removing the hemiacetal hydroxyl group from the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide.... - group or nucleotidyl- group
Phosphatase	Hydrolase (EC 3)	P-B + H-OH P-OH + H-B
Kinase	Transferase (EC 2.7.1-2.7.4)	P-B + H-A P-A + H-B	transfer group = P
P = phosphonate Phosphonate Phosphonates or phosphonic acids are organic compounds containing C-PO2 or C-PO2 groups . Bisphosphonates were first synthesized in 1897 by Von Baeyer and Hofmann. An example of such a bisphosphonate is HEDP . Since the work of Schwarzenbach in 1949, phosphonic acids are known as effective...  group, OP = phosphate group, H-OP or P-OH = inorganic phosphate

Types

The phosphorylases fall into the following categories:

• Glycosyltranferases (EC 2.4)
  • Enzymes that break down glucan
    Glucan
    A glucan molecule is a polysaccharide of D-glucose monomers linked by glycosidic bonds.Many beta-glucans are medically important.-Types:The following are glucans:-Alpha:...
    
    s by removing a glucose residue (break O-glycosidic bond)
    • glycogen phosphorylase
      Glycogen phosphorylase
      Glycogen phosphorylase is one of the phosphorylase enzymes . Glycogen phosphorylase catalyzes the rate-limiting step in the degradation of glycogen in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond...
      
      
    • starch phosphorylase
      Starch phosphorylase
      Starch phosphorylase is a form of phosphorylase similar to glycogen phosphorylase, except that it acts upon starch instead of glycogen.The plant alpha-glucan phosphorylase, commonly called starch phosphorylase , is largely known for the phosphorolytic degradation of starch...
      
      
    • maltodextrin phosphorylase
  • Enzymes that break down nucleoside
    Nucleoside
    Nucleosides are glycosylamines consisting of a nucleobase bound to a ribose or deoxyribose sugar via a beta-glycosidic linkage...
    
    s into their constituent bases and sugars (break N-glycosidic bond)
    • Purine nucleoside phosphorylase
      Purine nucleoside phosphorylase
      Purine nucleoside phosphorylase also known as PNPase and inosine phosphorylase is an enzyme that in humans is encoded by the NP gene.- Function :Purine nucleoside phosphorylase is an enzyme involved in purine metabolism...
      
       (PNPase)
• Nucleotidyltransferases (EC 2.7.7)
  • Enzymes that have phosphorolytic 3' to 5' exoribonuclease activity (break phosphodiester bond)
    • RNase PH
      RNase PH
      RNase PH is an 3'-5' exoribonuclease and nucleotidyltransferase, present in archaea and bacteria, that is involved in tRNA processing. Contrary to hydrolytic enzymes, it is a phosphorolytic enzyme, meaning that it uses inorganic phosphate as a cofactor to cleave nucleotide-nucleotide bonds,...
      
      
    • Polynucleotide Phosphorylase
      Polynucleotide phosphorylase
      Polynucleotide Phosphorylase is a bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3'-terminal oligonucleotide polymerase activity. It is involved on mRNA processing and degradation in bacteria, plants, and in humans.In humans, the enzyme is encoded by the gene...
      
       (PNPase)

All known phosphorylases share catalytic and structural properties http://www.expasy.org/cgi-bin/nicedoc.pl?PDOC00095.

Activation

Phosphorylase a is the active form of glycogen phosphorylase that is derived from the phosphorylation of the inactive form, phosphorylase b.

Pathology

Some disorders are related to phosphorylases:

• Glycogen storage disease type V
  Glycogen storage disease type V
  Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase. Its incidence is reported as 1 in 100,000, approximately the same as glycogen storage disease type I....
  
   - muscle glycogen
• Glycogen storage disease type VI
  Glycogen storage disease type VI
  Glycogen storage disease type VI is a type of glycogen storage disease caused by a deficiency in liver glycogen phosphorylase or other components of the associated phosphorylase cascade system.It is also known as "Hers' disease", after Henri G...
  
  - liver glycogen

External links

• Muscle phosphorylase deficiency - McArdle's Disease Website