2-(Oxalylamino)-Benzoic Acid Is a General, Competitive Inhibitor of Protein-tyrosine Phosphatases

Abstract

Protein-tyrosine phosphatases (PTPs) are critically involved in regulation of signal transduction processes. Members of this class of enzymes are considered attractive therapeutic targets in several disease states, e.g. diabetes, cancer, and inflammation. However, most reported PTP inhibitors have been phosphorus-containing compounds, tight binding inhibitors, and/or inhibitors that covalently modify the enzymes. We therefore embarked on identifying a general, reversible, competitive PTP inhibitor that could be used as a common scaffold for lead optimization for specific PTPs. We here report the identification of 2-(oxalylamino)-benzoic acid (OBA) as a classical competitive inhibitor of several PTPs. X-ray crystallography of PTP1B complexed with OBA and related non-phosphate low molecular weight derivatives reveals that the binding mode of these molecules to a large extent mimics that of the natural substrate including hydrogen bonding to the PTP signature motif. In addition, binding of OBA to the active site of PTP1B creates a unique arrangement involving Asp 181 , Lys 120 , and Tyr 46 . PTP inhibitors are essential tools in elucidating the biological function of specific PTPs and they may eventually be developed into selective drug candidates. The unique enzyme kinetic features and the low molecular weight of OBA makes it an ideal starting point for further optimization.

Structure-based Design of Selective and Potent Inhibitors of Protein-tyrosine Phosphatase β

“…Cloning of the catalytic domains of PTP1B, PTP␤, GLEPP1 (residues 885-1188), PTP␣ domain 1, and CD45 domain 1-2 were performed as described previously (28,30). The PTP LAR expression vector was a kind gift from M. Streuli, Boston.…”

“…compound A, Fig. 1) (28). The key structural features of OBA are two carboxyl groups bound, directly and through a carbonylamino group, to an aromatic ring.…”

Generation of inhibitor-sensitive protein tyrosine phosphatases via active-site mutations

“…Active-site structural comparison of PTP1B and HePTP. The protein surfaces of PTP1B (A, PDB: 1C83 [38]) and HePTP (B, PDB: 1ZC0 [49]) are shown in gray, with the portions of the surface comprising V49/I107 shown in green and the portions comprising I219/I274 shown in red. For perspective, the active-site catalytic cysteine residues of PTP1B and HePTP are shown in yellow.…”

“…This general PTP inhibitor, which was discovered by workers at Novo Nordisk, inhibits a variety of classical PTPs at micromolar concentrations (PTP1B, PTP α , PTP β , PTP ε , CD45, SHP-1) [38]. Also, the crystal structure of 1 bound to PTP1B has been reported [38]. Importantly, the indole nitrogen of 1 binds close in space to V49 and I219.…”

“…As a starting point for a panel of rationally designed allele-specific inhibitors that meet these criteria, we chose 6-(oxalyl-amino)-1H-indole-5-carboxylic acid (compound 1, Figure 3) as a scaffold. This general PTP inhibitor, which was discovered by workers at Novo Nordisk, inhibits a variety of classical PTPs at micromolar concentrations (PTP1B, PTP α , PTP β , PTP ε , CD45, SHP-1) [38]. Also, the crystal structure of 1 bound to PTP1B has been reported [38].…”