Hydrogen peroxide is a product of oxygen consumption by Trichomonas vaginalis

The amitochondriate sexually-transmitted human parasitic protozoan Trichomonas vaginalis (Bushby strain) grown anaerobically on complex medium containing cysteine and ascorbic acid consumed O-2 avidly (6.9 mu M min(-1) per 10(6) organisms) with an apparent K-m value of 5.1 mu M O-2: O-2 uptake was inhibited by O-2 > 120 mu M. Spectrophotometric assays in the presence of microperoxidase (419-407 nm) indicated that H2O2 was produced and that inhibition by high O-2 concentrations was again evident. Hydrogenosomes oxidizing pyruvate in the presence of ADP and succinate showed similar patterns of O-2 consumption, H2O2 production (33.5 pmol min(-1) per mg protein), and O-2 inhibition. Cytosolic NADH oxidase gave no detectable H2O2, whereas the cytosolic NADPH oxidase produced H2O2 at a rate (43 pmol min(-1) per mg protein) greater than that of hydrogenosomes. These results are discussed in relation to the oxidative stress experienced by the pathogen in its natural habitat.