|PDB structures||RCSB PDB PDBe PDBsum|
- A-B + P ⇌ A + P-B
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|
(EC 2.4 and EC 2.7.7)
|A-B + H-OP ⇌ A-OP + H-B||transfer group = A = glycosyl- group or|
|P-B + H-OH ⇌ P-OH + H-B|
|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:
- Glycosyltransferases (EC 2.4)
- Enzymes that break down glucans by removing a glucose residue (break O-glycosidic bond)
- Enzymes that break down nucleosides into their constituent bases and sugars (break N-glycosidic bond)
- Purine nucleoside phosphorylase (PNPase)
- Nucleotidyltransferases (EC 2.7.7)
All known phosphorylases share catalytic and structural properties .
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:
- Lehninger Principles of Biochemistry 5th ed. pg. 603
- Muscle phosphorylase deficiency - McArdle's Disease Website
- Phosphorylases at the US National Library of Medicine Medical Subject Headings (MeSH)