Table I.
Characteristics and activities of Prxs that are expressed in Arabidopsis leaves
| prx | MATDB Entry | Targeting | No. of Amino Acid Residues | Molecular Mass | pI | Activity with DTT | Activity with Trx |
|---|---|---|---|---|---|---|---|
| kD | mol H2O2 mol Prx min−1 | ||||||
| 2-Cys Prx A | At3g11630 | Chloroplasts | 266 | 29.1 | 4.91 | 1 ± 1 | 6.5 ± 0.5 |
| 2-Cys Prx B | At5g06290 | Chloroplasts | 271 | 29.6 | 4.71 | 6 ± 1 | 7.8 ± 0.6 |
| Prx II B | At1g65980 | Cytosol | 162 | 17.4 | 5.17 | 150 ± 12 | – |
| Prx II C | At1g65970 | Cytosol | 162 | 17.4 | 5.33 | 156 ± 5 | 0.8 ± 0.3 |
| Prx II E | At3g52960 | Chloroplasts | 234 | 24.7 | 5.03 | 57 ± 5 | – |
| Prx II F | At3g06050 | Mitochondria | 199 | 21.2 | 6.29 | 70 ± 5 | – |
| prx Q | At3g26060 | Chloroplasts | 215 | 23.6 | 5.53 | – | – |
The H2O2 reducing activities of heterologously expressed 2-Cys Prx A and B, and Prx II B, C, E and F were determined in a non-physiological activity assay using dithiothreitol (DTT) as electron donor for regeneration of reduced Prx protein. A decrease in H2O2 concentration was measured after formation of colored Fe(III)isothiocyanate at 480 nm. In an enzymatic, Trx-dependent activity assay, NADPH was used as electron donor and the decrease in absorbance at 340 nm was monitored (mean ± se of n ≥ 7 determinations). MATDB, MIPS Arabidopsis thaliana database.