Table 1.
Features of Arabidopsis APK Isoforms
| Isoform | AGI Code | TargetP Prediction/Score | ChloroP Predicted TP Length | MW with Target Peptide | MW without Target Peptide | Km[APS] | Vmax |
|---|---|---|---|---|---|---|---|
| APK1 | At2g14750 | Chloroplast 0.735 | 38 aa | 29.8 kD | 25.9 kD | 5.3 μM | 20.1 units mg protein−1 |
| APK2 | At4g39940 | Chloroplast 0.548 | 59 aa | 32.0 kD | 25.8 kD | 1.0 μM | 10.6 units mg protein−1 |
| APK3 | At3g03900 | Other 0.752 | – | n/a | 23.1 kD | 7.4 μM | 12.4 units mg protein−1 |
| APK4 | At5g67520 | Chloroplast 0.653 | 75 aa | 32.8 kD | 26.3 kD | 2.1 μM | 12.7 units mg protein−1 |
The subcellular localization of APK and the prediction of transite peptide cleavage sites were determined by the web-based program TargetP. The Km and Vmax values were calculated from enzyme activity data obtained with varied (0.5 to 10 μM) concentrations of APS using the standard Michaelis-Menten model. AGI, Arabidopsis Genome Initiative; TP, transite peptide; MW molecular weight; aa, amino acids.