DEFINITION
Proteins can undergo phosphorylation/dephosphorylation cycles able to modulate their activity in the minutes time range.
Protein kinases are enzymes that transfer a phosphate group from ATP to the hydroxyl group of serine/threonine or tyrosine.
Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins.
The Protein Kinase Resource UCSD
PKCs
