The oxidative mechanism of action of ortho-quinone inhibitors of protein-tyrosine phosphatase alpha is mediated by hydrogen peroxide.
Here, we report the identification and characterization of five ortho-quinone inhibitors of PTPalpha. We observed that the potency of these compounds in biochemical assays was markedly enhanced by the presence of DTT. A kinetic analysis suggested that they were functioning as irreversible inhibitors and that the inhibition was targeted to the catalytic site of PTPalpha. The inhibition observed by these compounds was sensitive to superoxide dismutase and catalase, suggesting that reactive oxygen species may be mediators of their inhibition. We observed that in the presence of DTT, these compounds would produce up to 2.5mM hydrogen peroxide (H(2)O(2)). The levels of H(2)O(2) produced were sufficient to completely inactivate PTPalpha. In contrast, without a reducing agent the compounds did not generate H(2)O(2) and showed little activity towards PTPalpha. In addition, these compounds inhibited PTPalpha-dependent cell spreading in NIH 3T3 cells at concentrations that were similar to their activity in biochemical assays. The biological implications of these results are discussed as they support growing evidence that H(2)O(2) is a key regulator of PTPs.
Drug Discovery, SUGEN Inc., 230 East Grand Avenue, South San Francisco, CA 94080, USA. michael.bova@elan.com
Michael P
MP
Bova
Matthew N
MN
Mattson
Stefan
S
Vasile
Danny
D
Tam
Leslie
L
Holsinger
Meire
M
Bremer
Terence
T
Hui
Gerald
G
McMahon
Audie
A
Rice
Jon M
JM
Fukuto
D000818:Animals; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D041681:NIH 3T3 Cells; D010084:Oxidation-Reduction; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D011809:Quinones / Q000737:chemistry* / Q000494:pharmacology*; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4
D011809:Quinones; D006861:Hydrogen Peroxide; D017027:Protein Tyrosine Phosphatases; C516843:Ptpra protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4