Phosphatase Antibodies

Antibodies for the Analysis of Phosphatases

During a phosphorylation reaction, a member of the kinase protein family adds a phosphate group to a serine, threonine or tyrosine residue of a target protein. This process can be reversed by another group of enzymes called phosphatases. Phosphatases can be classified into three groups: Ser/Thr phosphatases, Tyr phosphatases (PTP) and Asp-based protein phosphatases (Moorhead et al. 2007).

The activity of phosphatases can be regulated by other post-translational modifications, such as SUMOylation. An example is the SUMOylation of the protein-tyrosine phosphatase 1B (PTP1B) which has been reported to result in a reduction of its catalytic activity (Dadke et al. 2007).

Signaling of specific kinases, such as GSK3, can be inhibited with the help of kinase inhibitors (Cohen and Goedert 2004). Many kinase inhibitors have been successfully used for the treatment of various diseases, including cancer. When searching for the optimal kinase inhibitor for your experiment, we recommend you consult dedicated websites, like the "Kinase Inhibitor Database" hosted on the website of the “International Centre for Kinase Profiling”. In contrast to kinase inhibitors, phosphatase inhibitors like okadaic acid and microcystin act rather broadly by inhibiting entire phosphatase families. Due to this, phosphatases have been relatively neglected as potential therapeutic targets, although many are known biomarkers. For example, prostatic acid phosphatase (PAP) was one of the first identified tumor markers and used in clinical diagnostics for over 50 years for prostate cancer screening and staging (Mayo Clinic). It was replaced as the marker of choice in the 1980s by serum prostate specific antigen (PSA) (Taira et al. 2007).

Recent advances in the understanding of phosphatases have highlighted phosphatases as critical growth-regulatory molecules that represent a new class of therapeutic targets.

Antibodies for Phosphatase Research

Bio-Rad offers a variety of antibodies for analyzing phosphatase levels by ELISA, flow cytometry, immunofluorescence, immunohistochemistry and western blotting.

For your convenience, we have grouped our research reagents into the main phosphatase families:

• Protein Ser/Thr phosphatases – these enzymes catalyze the removal of phosphate groups from serine and/or threonine residues by mediating the hydrolysis of phosphoric acid monoesters. They can be further grouped into two categories: phosphoprotein phosphatases (PPP), and metallo-phosphatases (PPM), which require a divalent cation, commonly Mg²⁺, for their catalytic activity (Moorhead et al. 2007)
• Protein Tyr phosphatases (PTPs) – these enzymes are defined by a unique signature motif HC(X)₅R in which the cysteine is the essential residue for the catalysis step (Tonks 2006). They can be further grouped into two categories: tyrosine-specific PTPs that dephosphorylate protein substrates on tyrosine, and DSPs (dual-specificity phosphatases) that dephosphorylate protein substrates on tyrosine, serine and threonine residues as well as dephosphorylating lipid substrates (Tiganis and Bennett 2007)
• Asp-based protein phosphatases – these enzymes are defined by a unique signature motif DXDXT/V and use Asp as a nucleophile (Moorhead et al. 2007; Seifried et al. 2013)

References

• Cohen P and Goedert M (2004). GSK3 inhibitors: development and therapeutic potential. Nature Reviews Drug Discovery 3, 479-487.
• Dadke S et al. (2007). Regulation of protein tyrosine phosphatase 1B by sumoylation. Nat Cell Biol 9, 80-5.
• Mayo Clinic. Interpretive Handbook Test 8019: Prostatic Acid Phosphatase (PAP), Serum Clinical Information. http://www.mayomedicallaboratories.com/interpretive-guide/?alpha=P&unit_code=8019, accessed July 27, 2018.
• Moorhead GB et al. (2007). Emerging roles of nuclear protein phosphatases. Nat Rev Mol Cell Biol 8, 234-44.
• Seifried A (2013). Human HAD phosphatases: structure, mechanism, and roles in health and disease. FEBS J 280, 549-71.
• Taira A et al. (2007). Reviving the acid phosphatase test for prostate cancer. Oncology (Williston Park) 21, 1003-10.
• Tiganis T and Bennett AM (2007). Protein tyrosine phosphatase function: the substrate perspective. Biochem J 402, 1-15.
• Tonks NK (2006). Protein tyrosine phosphatases: from genes, to function, to disease. Nat Rev Mol Cell Biol 7, 833-46.