Phosphoprotein phosphatase

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Phosphoprotein phosphatase
Identifiers
EC number 3.1.3.16
CAS number 9025-75-6
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum

Phosphoprotein phosphatase is an enzyme that dephosphorylates certain phosphorylated proteins.[1]

In some contexts, "Phosphoprotein phosphatase" is equated with serine/threonine specific protein phosphatase, and classified under EC 3.1.3.16.[2]

In other contexts, the term also includes protein tyrosine phosphatase (EC 3.1.3.48) and dual-specificity phosphatase.[1][3] This latter convention is used in this article.

Overview of control of enzyme activity[edit]

The control of enzyme activity involves covalent modifications, including the addition of phosphate ions to serine, threonine and tyrosine residues in the enzyme. This addition is catalysed by protein kinases. The reverse reaction is carried out by phosphatase.

Effects of activation of phosphoprotein phosphatase[edit]

Phosphoprotein phosphatase is activated by the hormone insulin, which indicates that there is a high concentration of glucose in the blood. The enzyme then acts to dephosphorylate other enzymes, such as phosphorylase kinase, glycogen phosphorylase, and glycogen synthase.

This leads to phosphorylase kinase and glycogen phosphorylase's becoming inactive, while glycogen synthase is activated. As a result, glycogen synthesis is increased and glycogenolysis is decreased, and the net effect is for energy to enter and be stored inside the cell.

Mechanism[edit]

Phosphorylation involves the transfer of phosphate groups from ATP to the enzyme, the energy for which comes from hydrolysing ATP into ADP or AMP.

However, dephosphorylation releases phosphates into solution as free ions, because attaching them back to ATP would require energy input.

Examples[edit]

Human genes that encode proteins with phosphoprotein phosphatase activity include:

Protein serine/threonine phosphatase[edit]

Protein tyrosine phosphatase[edit]

Dual-specificity phosphatase[edit]

Ungrouped[edit]

References[edit]

  1. ^ a b Benjamin Lewin (2007). Cells. Jones & Bartlett Learning. pp. 625–. ISBN 978-0-7637-3905-8. Retrieved 20 December 2010. 
  2. ^ "ENZYME entry 3.1.3.16". Retrieved 2010-12-20. 
  3. ^ Robert Roskoski (1996). Biochemistry. Elsevier Health Sciences. pp. 430–. ISBN 978-0-7216-5174-3. Retrieved 20 December 2010. 

External links[edit]