Protein Phosphatase

Introduction
Protein phosphorylation constitutes to one of the major types of reversible post translational modifications that can regulate the stability, localization or the function of a particular protein.

Hydroxyl group containing amino acids such as Ser, Thr & Tyr are the sites of phosphorylation in proteins (approximately 86%, 12% and 8% of the phosphoproteome respectively).
Phosphorylation at these amino acid residues is catalyzed by a specific group of enzymes known as “PROTIEIN KINASES”.

Addition or removal of the phosphate group to a protein induces conformational change in its structure leading to the downstream events such as associating with a partner protein, translocation to the target cellular compartment or increase in its activity etc.

PROTEIN PHOSPHATASES are a class of catalytic proteins that mediate the elimination of a phosphate group from the phosphorylated amino acid residue of target proteins.
Dephosphorylation of proteins by the protein phosphatases is established as an ingenuous regulatory mechanism that regulates many key intracellular processes such as gene regulation, vesicular transport, respiration, cell proliferation and differentiation.

Aberrancies in kinase/phosphatase activity have been associated with many diseases, both genetic and metabolic, exposing protein phosphatases as future therapeutic targets.
Despite the high importance of this class of proteins, only few of them have been well studied.
This is in part due to the inadequacy of reagents like protein phosphatase inhibitors.

Figure 1. Role of phosphorylation in the modulation of protein function. As shown in the figure, phosphatases act antagonistically to kinases.
Phosphorylation activates the protein function in some proteins and represses in other proteins.

The reversible addition and removal of phosphate group from a target protein serves as an “on-and-off” button in the modulation of their activities.

In consistent with the importance of protein phosphorylation, a large portion of cellular proteins (almost 30%) undergo reversible phosphorylation and approximately 3% of the genome

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