Phosphoprotein phosphatase
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166108325
2007-10-21T19:20:03Z
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'''Phosphoprotein phosphatase''' is an [[enzyme]] which dephosphorylates certain phosphorylated proteins.
==Overview of control of enzyme activity==
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 kinase]]s. The reverse reaction is carried out by phosphatase.
==Effects of activation of phosphoprotein phosphatase==
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 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==
Phosphorylation involves the transfer of phosphate groups from [[adenosine triphosphate|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.
==External links==
* {{MeshName|Phosphoprotein+phosphatase}}
* {{EC number|3.1.3.16}}
[[Category:Enzymes]]
{{Enzyme-stub}}
{{Phosphatases}}
{{Glycogenesis and glycogenolysis}}