The significance of protein phosphorylation in regulating the function and activity of protein factors and enzymes is now well established. Analysis of the presence of such phosphorylation, and its attendant effects, is often aided by removal of the protein phosphate groups by phosphatases.
Specificity of Phosphate Removal
Protein phosphorylation can be found on tyrosine, serine and threonine residues. Depending on which phosphatase is chosen, phosphates can be removed from all of these residues, or from a subset thereof. In particular, phosphatases have been characterized as having activity toward serine and threonine residues, or toward tyrosine residues.
A comparison of protein serine/threonine phosphatase (PSP) to protein tyrosine phosphatase (PTP) specific activity gives a measure of the specificity of the phosphatase. Lambda Protein Phosphatase can be used to remove both serine/threonine and tyrosine phosphorylation. Lambda Protein Phosphatase has greater reactivity against phospho-serine/threonine residues, Calf Intestinal Phosphatase shows a preference for phosphotyrosine residues, and Antarctic Phosphatase has similar activity on both types of phosphorylation (1).
Barshevsky, T. (2008) New England Biolabs, unpublished results.