Figure 5.

AtACHTs activation of chloroplast target enzymes. A, The AtACHTs reacted with high efficiency with At-2-Cys PrxA in the presence of DTT. At-2-Cys PrxA (5 μm) was incubated with 2.5 μm of AtTrx-f1 (circles), AtACHT1 (triangles), AtACHT2a (diamonds), or AtACHT4a (rectangles) in the presence of 0.4 mm DTT. At-2-Cys PrxA alone (asterisk) was used as a control. The reduction of H₂O₂ was measured at different time points. B, The ACHTs did not react efficiently with At-2-Cys PrxA when GSH was used as a reductant. The assay was performed as in A, but DTT was replaced with 0.8 mm GSH. Symbols are as in A. C, The AtACHTs reacted poorly with AtMDH. DTT-dependent activation of AtMDH (1.5 μm) was carried out with 1 μm AtTrx-f1 or the different AtACHTs. AtMDH enzyme activity after reduction was measured by monitoring the initial rate of consumption of NADPH during reaction with the substrate oxaloacetate. Symbols are as in A.