Phosphorylation/Dephosphorylation: Protein Phosphatase Inhibitors | | | Table 1: Selected Inhibitors | Inhibitors | Related Resource
Phosphorylation and dephosphorylation of structural and regulatory proteins are major intracellular control mechanisms in eukaryotes. Protein kinases transfer a phosphate from ATP to a specific protein, typically at serine, threonine, or tyrosine residues. Phosphatases remove the phosphoryl group and restore the protein to its original dephosphorylated state. Hence, the phosphorylation-dephosphorylation cycle can be regarded as a molecular "on-off" switch.
Protein phosphatases (PPs) have been classified into three distinct categories: serine/threonine (Ser/Thr)- specific, tyrosine-specific, and dual-specificity phosphatases. Based on biochemical parameters, substrate specificity, and sensitivity to various inhibitors, Ser/Thr protein phosphatases are divided into two major classes. Type I phosphatases, which include PP1, can be inhibited by two heat-stable proteins known as Inhibitor-1 (I-1) and Inhibitor-2 (I- 2). They preferentially dephosphorylate the b-subunit of phosphorylase kinase. Type II phosphatases are subdivided into spontaneously active (PP2A), Ca2+- dependent (PP2B), and Mg2+-dependent (PP2C) classes of phosphatases. They are insensitive to heat-stable inhibitors and preferentially dephosphorylate the a-subunit of phosphorylase kinase.
Protein tyrosine phosphatases (PTPs) are relatively recent additions to the phosphatase family. They remove phosphate groups from phosphorylated tyrosine residues of proteins. PTPs display diverse structural features and play important roles in the regulation of cell proliferation, differentiation, cell adhesion and motility, and cytoskeletal function. They are either transmembrane receptor-like PTPs or cytosolic enzymes. Each PTP contains a highly conserved catalytic domain of about 240 residues that contains highly conserved arginine and cysteine residues at the catalytic domain. The diversity of PTPs is primarily due to the variety of non-catalytic regulatory sequences and targeting domains attached to both N- and C-termini.
 Another category of protein phosphatases is the dual specificity phosphatases (DSPs), which play a key role in the dephosphorylation of MAP kinases. Hence, they are also termed as MAP kinase phosphatases (MKPs). On the basis of predicted structures, MKPs have been divided into three subgroups. Group I contains DSP1, DSP2, DSP4, and DSP5; group II enzymes are DSP6, DSP7, DSP9, and DSP10; and group III consists of DSP8 and DSP16. All the DSPs share strong amino-acid sequence homology in their catalytic domains. The catalytic domain contains a highly conserved consensus sequence DX26(V/L)X(V/ I)HCXAG(I/V) SRSXT(I/V)XXAY(L/I)M, where X could be any amino acid. The three underlined amino acids are reported to be essential for the catalytic activity of DSPs. The cysteine is required for the nucleophilic attack on the phosphorus of the substrate and the formation of the thiol-phosphate intermediate. The conserved arginine binds the phosphate group of phosphotyrosine or phosphothreonine, enabling transition-state stabilization, and the aspartate enhances catalysis by protonating oxygen on the departing phosphate group. All DSPs contain two conserved regions, known as the CH2 domains, at their amino terminus, which are involved in substrate binding. In addition, they contain a MAP kinase-docking site at the amino terminus that consists of a cluster of positively charged amino acids. The corresponding docking site on MAP kinases consists of negatively charged residues indicating that electrostatic interactions are involved in binding of MAP kinases and MKPs. The group III DSPs also have an extended carboxy terminus containing PEST sequences (abundant in proline, glutamate, serine and threonine) that are commonly found in rapidly degrading proteins. Removal of PEST sequences results in their stabilization. | | | | | | | Table 1: Selected Protein Phosphatase Inhibitors | | Product | Cat. No. | MW | Comments | | AG 10 | | 170.2 | An inhibitor of GTPase activity of transducin (IC50 = 45 mM) that also acts as a competitive inhibitor of calcineurin (IC50 = 21 mM). | | bpV(bipy) | | 380.3 | Potent protein tyrosine phosphatase (PTP) inhibitor (Ki = 100 nM for insulin receptor dephosphorylation). | | bpV(HOpic) | | 419.3 | Potent protein tyrosine phosphatase (PTP) inhibitor. Also inhibits liver glucose-6-phosphatase (IC50 = 1.12 mM). | | bpV(phen) | | 404.3 | Potent protein tyrosine phosphatase (PTP) inhibitor. Exhibits 1000-fold potency over sodium orthovanadate. Also inhibits microsomal glucose-6-phosphatase (Ki = 960 nM). | | bpV(pic) | | 367.3 | Potent protein tyrosine phosphatase (PTP) inhibitor. Also inhibits microsomal glucose-6-phosphatase (Ki = 420 nM). | | Calcineurin Autoinhibitory Peptide | | 2930.4 | Specific calcineurin inhibitor (PP2B) (IC50 = 10 mM). | | Calcineurin Autoinhibitory Peptide, Cell-Permeable | | 3501.1 | A cell-permeable peptide composed of the calcineurin (CaN) autoinhibitory domain (AID) fused to a poly-arginine-based protein transduction domain (11R) that inhibits CaN phosphatase activity. | | Calyculin A | | 1009.2 | Cell-permeable. Phosphorylated polyketide. PP2A ~ PP1 >> PP2B (IC50 for PP2A = 0.5-1.0 nM and for PP1 = 2.0 nM). | | Cantharidic Acid | | 214.2 | Terpenoid. Has high selectivity for PP2A (IC50 = 50 nM). | | Cantharidin | | 196.2 | Cell-permeable. Terpenoid. PP2A > PP1 >> PP2B (IC50 for PP2A = 40 nM and for PP1 = 473 nM). | | CDC25 Phosphatase Inhibitor, BN82002 | | 359.4 | A potent, selective, irreversible inhibitor of CDC25 phosphatase family (IC50 = 2.4, 3.9, 6.3, 5.4, and 4.6 mM for 25A, 25B2, 25B3, 25C, and 25C-cat, respectively). | | CDC25 Phosphatase Inhibitor, NSC 663284 | | 321.8 | A potent, irreversible and mixed competitive inhibitor of the CDC25 phosphatase family (Ki = 29, 95 and 89 nM for CDC25A, CDC25B2 and CDC25C, respectively; IC50 = 210 nM for CDC25B2). | | Cyclosporin A | | 1202.6 | Binds to cyclophilin in cell; the complex inhibits PP2B with nanomolar affinity. | | Cypermethrin | | 416.3 | Potent inhibitor of PP2B (IC50 = 40 pM). | | DARPP-32 | | 32,000 | Potent inhibitor of PP1 (IC50 = 1-2 mM). | | DARPP-32, Phospho- | | 32,000 | Potent inhibitor of PP1 (IC50 = 1 nM). | | Deltamethrin | | 505.2 | Potent inhibitor of PP2B (IC50 = 100 pM). | | Dephostatin | | 168.2 | Protein tyrosine phosphatase (PTP) inhibitor (IC50 = 7.7 mM). | | 3,4-Dephostatin | | 168.2 | A protein tyrosine phosphatase inhibitor (IC50 = 18 mM) | | 3,4-Dephostatin, Ethyl- | | 182.2 | A more stable ethyl analog of the protein tyrosine phosphatase (PTP) inhibitor 3,4-Dephostatin (Cat. No. 263202). Potently inhibits PTP1B (IC50 = 580 ng/ml). | | 1,4-Dimethylendothall | | 214.2 | A useful negative control for Canthardic Acid (Cat. No. 210150), Canthardin (Cat. No. 210155), and Endothall (Cat. No. 324760). | | Endothall | | 186.2 | A specific inhibitor of PP2A (IC50 = 90 nM). | | Fenvalerate | | 419.9 | Potent inhibitor of PP2B (IC50 = 2-4 nM). | | Fostriecin | | 452.4 | A potent PP2A inhibitor (IC50 = 3.2 nM) Inhibits PP1 only at higher concentrations (IC50 = 131 mM). | | Microcystin-LF, Microcystis aeruginosa | | 986.2 | A more cell-permeable analog of Microcystin-LR (Cat. No. 475815). Useful for studies in intact cells. | Microcystin-LR,
Microcystis aeruginosa | | 995.2 | Cyclic peptide. PP2A ~ PP1 >> PP2B (IC 50 for PP2A = 40 pM and for PP1 = 1.7 nM). Does not enter some mammalian cells. See also Cat. No. 475821. | Microcystin-LW,
Microcystis aeruginosa | | 1025.2 | A more cell-permeable analog of Microcystin-LR (Cat. No. 475815). Useful for studies in intact cells. | Microcystin-RR,
Microcystis aeruginosa | | 1038.2 | Cyclic peptide. PP2A ~ PP1 >> PP2B (IC50 = 1.4 nM for PP2A). Does not enter some mammalian cells. | | mpV(pic) | | 257.1 | Potent PTP inhibitor. More potent for insulin receptor (IR) dephosphorylation than epidermal growth factor receptor (EGFR) dephosphorylation. | | a-Naphthyl Acid Phosphate | | 257.1 | Broad-spectrum protein phosphatase inhibitor. | | NIPP-1, His•Tag®, Bovine Thymus, Recombinant, E. coli | | 38,500 | A potent and specific inhibitor or protein phosphatase 1 (PP1; Ki = 1-10 pM) that can be used to distinguish PP1 from other major serine/threonine protein phosphatases, including PP2A, PP2B, and PP2C. | Okadaic Acid
Prorocentrum concavum | | 805.0 | Cell-permeable. PP2A > PP1 >> PP2B (IC 50 for PP2A = 100 pM; for PP1 = 10-15 nM; and for PP2B = 5 mM). See also Cat. No. 495609. | | Okadaic Acid, Ammonium Salt | | 822.0 | Cell-permeable. PP2A > PP1 >> PP2B. (IC50 for PP2A = 100 pM; for PP1 = 10-15 nM; and for PP2B = 5 mM). | | Okadaic Acid, Potassium Salt | | 843.1 | Cell-permeable. PP2A > PP1 >> PP2B. (IC50 for PP2A = 100 pM; for PP1 = 10-15 nM; and for PP2B = 5 mM). | | Okadaic Acid, Sodium Salt | | 827.0 | Cell-permeable. PP2A > PP1 >> PP2B. (IC50 for PP2A = 100 pM; for PP1 = 10-15 nM; and for PP2B = 5 mM). | | Phenylarsine Oxide | | 168.0 | Cell-permeable PTP inhibitor (IC50 = 18 mM) | | Protein Phosphatase Inhibitor 2, Human, Recombinant | | 30,000 | Potent inhibitor of the free catalytic subunit of PP1 (IC50 = 1 nM). | | Protein Phosphatase Inhibitor 2, Rabbit Muscle, Recombinant | | 22,800 | Inhibits the catalytic subunit of PP1 (IC50 = 2 nM). | | Protein Phosphatase Inhibitor 2, Human, Recombinant, E. coli | | 30,000 | Inhibitor-2 is the regulatory subunit of the cytosolic type 1 Ser/Thr protein phosphatase-1 (PP1). It potently inhibits the activity of the free catalytic subunit of PP1 (IC50 = 100 pM). | | Protein Phosphatase 2A Inhibitor I1PP2A, Human, Kidney, Recombinant, E. coli | | 3000 | Potently inhibits all forms of PP2A (Ki ~ 0.1 nM). | | Protein Phosphatase 2A Inhibitor I2PP2A, Human, Recombinant, E. coli | | 39,000 | Potently inhibits PP2A (Ki ~ 0.100 pM) | Protein Tyrosine Phosphatase CD45
Inhibitor | | 307.3 | A cell-permeable pivalamide with a 9,10-phenanthrenedione core that displays antiproliferative properties. Acts as a potent, selective, competitive, and reversible inhibitor of CD45 (IC50 = 200 nM, 3.8 mM for CD45 lck, > 30 mM for PTP1B lck). | | Protein Tyrosine Phosphatase Inhibitor I | | 215.1 | A potent, cell-permeable, and covalent PTP inhibitor. Inhibits SHP-1 (DSH2) (Ki = 43 mM) and PTP1B (Ki = 42 mM). | | Protein Tyrosine Phosphatase Inhibitor II | | 229.1 | A potent, cell-permeable, and covalent PTP inhibitor. Binds to SHP-1 ( DSH2) with lower affinity than PTP inhibitor I (Cat. No. 540200). | | Protein Tyrosine Phosphatase Inhibitor III | | 273.1 | A potent, cell-permeable, and covalent PTP inhibitor. Binds to SHP-1 ( DSH2) with lower affinity (K i = 193 mM) than PTP inhibitor I (Cat. No. 540200). | | Protein Tyrosine Phosphatase Inhibitor IV | | 608.6 | A potent, reversible, substrate competitive, active-site-directed inhibitor of protein tyrosine phosphatases (PTP). Reported to inhibit SHP-2 (IC50 = 1.8 mM), PTP1B (IC50 = 2.5 mM), PTP-e (IC50 = 8.4 mM), PTP-Meg-2 (IC50 = 13 mM), PTP-s (IC50 = 20 mM), PTP-b (IC50 = 6.4 mM), and PTP-m (IC50 = 6.7 mM). | | PTP1B Inhibitor | | 741.5 | A cell-permeable, selective, non-competitive, reversible inhibitor of PTP1B (IC50 = 4 mM and 8 mM for PTP1B403 and PTP1B298, respectively). | | RK-682 | | 368.5 | A specific non-call-permeable inhibitor of PTP. Inhibits dephosphorylation activity of CD45 (IC50 = 54 mM) and VHR (IC50 = 2.0 mM) in vitro. | | Sodium Orthovanadate | | 183.9 | A broad spectrum inhibitor of protein tyrosine phosphatases. | | Sodium Stibogluoconate | | 907.9 | An irreversible inhibitor of protein tyrosine phosphatases, including Src homology PTPase-1 (SHP-1). Exhibits anti-leishmanial properties. At higher concentrations, inhibits SHP-2 and PTP1B activities. | | Suramin | | 1429.2 | Useful as a reversible and competitive inhibitor of protein tyrosine phosphatases. | | Tautomycin | | 767.0 | Inhibits PP1 (IC50 = 1 nM), PP2A (IC50 = 10 nM), and smooth muscle endogenous phosphatase (IC50 = 6 nM). |
| | | | Inhibitors: Protein Phosphatase |
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| bpV(bipy) |
203694 |
| bpV(HOpic) |
203701 |
| bpV(phen) |
203695 |
| bpV(pic) |
203705 |
| Calcineurin Autoinhibitory Peptide |
207000 |
| Calcineurin Autoinhibitory Peptide, Cell-permeable |
207001 |
| Calyculin A, Discodermia calyx |
208851 |
| Cantharidic Acid |
210150 |
| Cantharidin |
210155 |
| CDC25 Phosphatase Inhibitor I, BN82002 |
217691 |
| CDC25 Phosphatase Inhibitor II, NSC 663284 |
217692 |
| CDC25 Phosphatase Inhibitor III, BN82685, Benzoate Salt |
217693 |
| Cyclosporin A, Tolypocladium inflatum |
239835 |
| Cypermethrin |
239900 |
| DARPP-32, Phospho-, Rat, Recombinant, E. coli |
251756 |
| DARPP-32, Rat, Recombinant, E. coli |
251755 |
| Deltamethrin |
253300 |
| Dephostatin |
263200 |
| 3,4-Dephostatin |
263202 |
| 3,4-Dephostatin, Ethyl- |
263203 |
| 1,4-Dimethylendothall |
311250 |
| eIF-2a Inhibitor, Salubrinal |
324895 |
| Endothall |
324760 |
| FBPase-1 Inhibitor |
344267 |
| Fenvalerate |
341380 |
| Fostriecin, Sodium Salt, Streptomyces pulveraceous |
344280 |
| b-Glycerophosphate, Disodium Salt, Pentahydrate |
35675 |
| Microcystin-LF, Microcystis aeruginosa |
475814 |
| Microcystin-LR, Microcystis aeruginosa |
475815 |
| InSolution™ Microcystin-LR, Microcystis aeruginosa |
475821 |
| Microcystin-LW, Microcystis aeruginosa |
475818 |
| Microcystin-RR, Microcystis aeruginosa |
475816 |
| mpV(pic) |
475950 |
| a-Naphthyl Acid Phosphate, Monosodium Salt |
479775 |
| NFAT Activation Inhibitor III |
480403 |
| NIPP-1, His•Tag®, Bovine Thymus, Recombinant, E. coli |
482251 |
| InSolution™ Nodularin, Nodularia spumigena |
488003 |
| Okadaic Acid, Prorocentrum sp. |
495604 |
| InSolution™ Okadaic Acid, Prorocentrum sp. |
495609 |
| Okadaic Acid, Ammonium Salt |
459616 |
| Okadaic Acid, Potassium Salt |
459618 |
| Okadaic Acid, Sodium Salt |
459620 |
| Phenylarsine Oxide |
521000 |
| Phosphatase Inhibitor Cocktail Set I |
524624 |
| Phosphatase Inhibitor Cocktail Set II |
524625 |
| PP2A Inhibitor I, GST-Fusion, Human Kidney, Recombinant, E. coli |
539552 |
| PP2A Inhibitor I, GST-Fusion, Human, Recombinant, E. coli |
539620 |
| PPI2, Human, Recombinant, E. coli |
539638 |
| PPI2, Rabbit Muscle, Recombinant, E. coli |
539516 |
| PTP CD45 Inhibitor |
540215 |
| PTP Inhibitor II |
540205 |
| PTP Inhibitor III |
540210 |
| PTP Inhibitor IV |
540211 |
| Phosphotyrosine Phosphatase Inhibitor Set (Vanadium) |
525325 |
| PRL-3 Inhibitor |
539808 |
| Protein Phosphatase Inhibitor Set II |
539630 |
| Protein Tyrosine Phosphatase Inhibitor I |
540200 |
| PTP1B Inhibitor |
539741 |
| RK-682, Streptomyces sp. |
557322 |
| Sodium Orthovanadate |
567540 |
| Sodium Stibogluconate |
567565 |
| Suramin, Sodium Salt |
574625 |
| InSolution™ Tautomycetin, S. griseochromogenes |
580550 |
| Tautomycin, Streptomyces spiroverticillatus |
580551 |
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| | | | Other Related Resource | | Phosphatase Inhibitor Cocktails | | | | | |
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