Inhibition of indoleamine 2,3 dioxygenase activity by H2O2

Anne Poljak*, Ross Grant, Chris J D Austin, Joanne F. Jamie, Robert D. Willows, Osamu Takikawa, Tamantha K. Littlejohn, Roger J W Truscott, Mark J. Walker, Perminder Sachdev, George A. Smythe

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Indoleamine 2,3-dioxygenase is the first and rate limiting enzyme of the kynurenine pathway of tryptophan metabolism, has potent effects on cell proliferation and mediates antimicrobial, antitumorogenic, and immunosuppressive effects. As a potent cytotoxic effector, the mechanisms of indoleamine 2,3-dioxygenase inhibition deserve greater attention. The work presented here represents the first systematic study exploring the mechanisms by which low levels of hydrogen peroxide (10-100 μM) inhibit indoleamine 2,3-dioxygenase in vitro. Following brief peroxide exposure both enzyme inhibition and structural changes were observed. Loss of catalysis was accompanied by oxidation of several cysteine residues to sulfinic and sulfonic acids, observed by electrospray and MALDI mass spectrometry. Enzyme activity could in part be preserved in the presence of sulfhydryl containing compounds, particularly DTT and methionine. However, these structural alterations did not prevent substrate (l-tryptophan) binding. Some enzyme activity could be recovered in the presence of thioredoxin, indicating that the inhibitory effect of H2O2 is at least partially reversible in vitro. We present evidence that cysteine oxidation represents one mechanism of indoleamine 2,3-dioxygenase inhibition. Crown

Original languageEnglish
Pages (from-to)9-19
Number of pages11
JournalArchives of Biochemistry and Biophysics
Volume450
Issue number1
DOIs
Publication statusPublished - 1 Jun 2006

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