(1-4)-alpha-D-glucan:phosphate alpha-D-glucosyltransferase

EC no.
CAS no.9035-74-9
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum

In biochemistry, 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 enzymes that catalyze the production of glucose-1-phosphate from a glucan such as glycogen, starch or maltodextrin.

Phosphorylase is also a common name used for glycogen phosphorylase in honor of Earl W. Sutherland Jr., who in the late 1930s discovered it as the first phosphorylase.[1]


Phosphorylases should not be confused with phosphatases, which remove phosphate groups. 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 (a hydrolase) or a kinase (a phosphotransferase). A phosphatase removes a phosphate group from a donor using water, whereas a kinase transfers a phosphate 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- 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 group, OP = phosphate group, H-OP or P-OH = inorganic phosphate


The phosphorylases fall into the following categories:

All known phosphorylases share catalytic and structural properties.[2]


Phosphorylase a is the more active R form of glycogen phosphorylase that is derived from the phosphorylation of the less active R form, phosphorylase b with associated AMP. The inactive T form is either phosphorylated by phosphoylase kinase and inhibited by glucose, or dephosphorylated by phosphoprotein phosphatase with inhibition by ATP and/or glucose 6-phosphate. Phosphorylation requires ATP but dephosphorylation releases free inorganic phosphate ions.


Some disorders are related to phosphorylases:

See also[]


  1. ^ Nelson DL, Lehninger AL, Cox MM (2005). Lehninger Principles of Biochemistry (5th ed.). W. H. Freeman. p. 603. ISBN 978-0-7167-4339-2.
  2. ^ "PROSITE documentation PDOC00095 [for PROSITE entry PS00102]". PROSITE.

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