| Phosphorylase | |
| Ec Number: | 2.4.1.1 |
| Cas Number: | 9035-74-9 |
| Width: | 270 |
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: