1887

Abstract

and are microaerophilic protozoa which rely on fermentative metabolism for energy generation. These organisms have developed a number of antioxidant defence strategies to cope with elevated O tensions which are inimical to survival. In this study, the ability of pyruvate, a central component of their energy metabolism, to act as a physiological antioxidant was investigated. The intracellular pools of 2-oxo acids in were determined by HPLC. With the aid of a dichlorodihydrofluorescein diacetate-based assay, intracellular reactive oxygen species generation by and suspensions was monitored on-line. Addition of physiologically relevant concentrations of pyruvate to and cell suspensions was shown to attenuate the rate of HO- and menadione-induced generation of reactive oxygen species. In addition, pyruvate was also shown to decrease the generation of low-level chemiluminescence arising from the oxygenation of anaerobic suspensions of . In contrast, addition of pyruvate to suspensions of respiring was shown to increase the generation of reactive oxygen species. These data suggest that (i) in and , pyruvate exerts antioxidant activity at physiological levels, and (ii) it is the absence of a respiratory chain in the diplomonads which facilitates the observed antioxidant activity.

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2001-12-01
2020-01-29
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