Protein phosphorylation and dephosphorylation

Enzyme activity can be modulated by the post-translational covalent modification of an enzyme. An example of one such modification is the phosphorylation or dephosphorylation of an enzyme. This kind of modification has been shown to be particularily important is the modulating the activity of proteins involved in cell cycle regulation, glucose metabolism and signal transduction.

In the case where an inactive enzyme is activated by phosphorylation, one has the following situation:

• the inactive enyme is not phosphorylated

• the substrate does not bind to the enzyme

• as a result of some kind of stimulus the inactive enzyme becomes phosphorylated

• after the enzyme is phosphorylated it undergoes a conformational shift and becomes active which means that substrate can bind to the enzyme

• since substrate can bind to the active site, catalysis can occur

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