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Updated: Jun 4, 2026

Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
Published on: February 24, 2018
IDENTIFICATION OF CONOIDIN A AS A COVALENT INHIBITOR OF PEROXIREDOXIN II
Jeralyn D Haraldsen1, Gu Liu, Catherine H Botting
1Department of Microbiology and Molecular Genetics, 316 Stafford Hall, University of Vermont, 95 Carrigan Drive, Burlington VT 05405, USA.
Abstract:
Conoidin A (1) is an inhibitor of host cell invasion by the protozoan parasite Toxoplasma gondii. In the course of studies aimed at identifying potential targets of this compound, we determined that it binds to the T. gondii enzyme peroxiredoxin II (TgPrxII). Peroxiredoxins are a widely conserved family of enzymes that function in antioxidant defense and signal transduction, and changes in PrxII expression are associated with a variety of human diseases, including cancer. Disruption of the TgPrxII gene by homologous recombination had no effect on the sensitivity of the parasites to 1, suggesting that TgPrxII is not the invasion-relevant target of 1. However, we showed that 1 binds covalently to the peroxidatic cysteine of TgPrxII, inhibiting its enzymatic activity in vitro. Studies with human epithelial cells showed that 1 also inhibits hyperoxidation of human PrxII. These data identify Conoidin A as a novel inhibitor of this important class of antioxidant and redox signaling enzymes.
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