Phosphoprotein phosphatase 3247263 166108325 2007-10-21T19:20:03Z 81.42.236.213 '''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}}