Figure 5.
pKa determination of the catalytic cysteine of poplar GrxC1, C2, C3, and C4. Reduced GrxC1 (A), GrxC2 (B), GrxC3 (C), and GrxC4 (D) WT proteins were incubated in different buffers ranging from pH 2.0 to 7.0 in presence or not of iodoacetamide (IAM) prior to measurement of their activity by using the HED assay. The percentages of remaining activity at each pH were determined by comparing the activity of the enzyme incubated with and without IAM and an adaptation of the Henderson–Hasselbach equation was used for pKa value determination. The data are represented as mean ± SD of three separate experiments.