Phosphorylase | |||||||||
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Identifiers | |||||||||
EC no. | 2.4.1.1 | ||||||||
CAS no. | 9035-74-9 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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In biochemistry, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor.
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 |
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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:
2.7.1-2.7.4: phosphotransferase/kinase (PO4) |
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2.7.6: diphosphotransferase (P2O7) | |||||||||||||||
2.7.7: nucleotidyltransferase (PO4-nucleoside) |
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2.7.8: miscellaneous |
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2.7.10-2.7.13: protein kinase (PO4; protein acceptor) |
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2.4.1: Hexosyl- transferases |
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2.4.2: Pentosyl- transferases |
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2.4.99: Sialyl transferases |
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