Role of Trypanosoma cruzi peroxiredoxins in mitochondrial bioenergetics.

Trypanosoma cruzi cytosolic (TcCPx) and mitochondrial tryparedoxin peroxidase (TcMPx) play a fundamental role in H(2)O(2) detoxification. Herein, mitochondrial bioenergetics was evaluated in cells that overexpressed TcCPx (CPx) and TcMPx (MPx) and in pTEX. In MPx, a higher expression was observed for TcCPx, and the same correlation was true for CPx. Differences in H(2)O(2) release among the overexpressing cells were detected when the mitochondrial respiratory chain was inhibited using antimycin A or thenoyltrifluoroacetone. MPx had higher O(2) consumption rates than pTEX and CPx, especially in the presence of oligomycin. In all of the cells, the mitochondrial membrane potential and the ATP levels were similar. Because of the mild uncoupling that was observed in MPx, the presence or induction of a proton transporter in the mitochondrial membrane is suggested when TcMPx is expressed at higher levels. Our results show a possible interplay between the cytosolic and mitochondrial antioxidant systems in a trypanosomatid.

Products of anaerobic metabolism in waterlogged roots of soybean are exported in the xylem.

Waterlogging leads to hypoxia of the root system. Metabolic changes occur that enable the plant to tolerate the hypoxic stress. We investigated the export of organic acids, products of anaerobic metabolism, via xylem of waterlogged soybean (Glycine max) plants. Organic acids were quantified by GC-MS and their formation via aspartate metabolism investigated using [4-13C]aspartate. Elevated levels of malate were found together with variable amounts of other organic acids, notably lactate and succinate. Addition of [4-13C]aspartate to the medium led to isotopic enrichment of several organic acids in the xylem sap. Quantitatively, malate carried the highest amount of label among the organic acids. Labelling of succinate indicates its formation by reversal of the TCA-cycle from oxaloacetate. Since aspartate was a prominent amino acid of the phloem sap, it is suggested that this is an important source of malate exported in the xylem. The export of these organic acids will play the role of removing electrons from the hypoxic roots, representing an additional mechanism in the metabolic response to root hypoxia. Malate, normally considered an intermediate in succinate formation, is definitively a product of anaerobic metabolism.