Detection and characterization of a glutathione conjugate of ochratoxin A.

Journal Article (Journal Article)

The ability of the carcinogenic mycotoxin ochratoxin A (OTA) to react with reduced glutathione (GSH) has been assessed using electrospray ionization (ES)-MS techniques. On the basis of the assumption that OTA undergoes biotransformation into the reactive quinone species OTQ (6), a synthetic sample of the reduced form of OTQ (6), hydroquinone OTHQ (5), was prepared and photoreacted with 6 M equiv of GSH to yield an authentic sample of the conjugate 8 that was definitively identified by mass spectrometry, UV-vis spectroscopy and NMR. With the authentic sample of 8 in hand, it was demonstrated that the same conjugate is produced from reaction of 100 microM OTA (1) in the presence of 5 mM GSH following incubation for 1 h with either horseradish peroxidase (HRP)/H(2)O(2), rat liver microsomes (RLM)/NADPH or free Fe(II). In each of these oxidative systems the conjugate 8 was generated in less than 1% yield and the parent OTA molecule is poorly metabolized. Comparison of the peak area ratio of the conjugate 8 to that for the hydroxyOTA metabolite from the RLM/NADPH system implied that the conjugate was produced at a rate of approximately 1-3 pmol min(-)(1) (mg of protein)(-)(1). These studies are the first to demonstrate that OTA undergoes biotransformation to a reactive intermediate [OTQ (6)] that covalently reacts with GSH to yield the conjugate 8. The biological implications of the reactivity of OTA toward GSH are discussed.

Full Text

Duke Authors

Cited Authors

  • Dai, J; Park, G; Wright, MW; Adams, M; Akman, SA; Manderville, RA

Published Date

  • December 2002

Published In

Volume / Issue

  • 15 / 12

Start / End Page

  • 1581 - 1588

PubMed ID

  • 12482240

International Standard Serial Number (ISSN)

  • 0893-228X

Digital Object Identifier (DOI)

  • 10.1021/tx0255929


  • eng

Conference Location

  • United States