| Isoenzyme | Km | Vmax (nkat mg−1 protein) | ||||
| Glu (mM) | NH4+ (μM) | ATP (μM) | Glu | NH4+ | ATP) | |
| OsGS1;1 | 1.9±0.0 | 27±5 | 450±20 | 190.0±12.3 | 186.3±18.4 | 170.2±15.1 |
| OsGS1;2 | 2.1±0.0 | 73±2 | 530±80 | 97.4±9.0 | 98.1±1.7 | 109.1±14.8 |
| AtGS1;1 | 1.1±0.4 | <10 | 300±20 | 29.3±1.6 | 27.4±0.7 | 21.4±0.4 |
| AtGS1;2 | 3.8±0.2 | 2450±150 | 1100±140 | 65.7±0.2 | 65.7±1.1 | 66.6±4.4 |
| AtGS1;3 | 3.9±0.1 | 1210±40 | 850±30 | 162±24 | 93.9±10 | 100.0±0.04 |
| AtGS1;4 | 0.6±0.1 | 48±6 | 400±50 | 79.2±1 | 65.7±1.5 | 73.9±4.2 |
| Isoenzyme | Km | Vmax (nkat mg−1 protein) | ||||
| Glu (mM) | NH4+ (μM) | ATP (μM) | Glu | NH4+ | ATP) | |
| OsGS1;1 | 1.9±0.0 | 27±5 | 450±20 | 190.0±12.3 | 186.3±18.4 | 170.2±15.1 |
| OsGS1;2 | 2.1±0.0 | 73±2 | 530±80 | 97.4±9.0 | 98.1±1.7 | 109.1±14.8 |
| AtGS1;1 | 1.1±0.4 | <10 | 300±20 | 29.3±1.6 | 27.4±0.7 | 21.4±0.4 |
| AtGS1;2 | 3.8±0.2 | 2450±150 | 1100±140 | 65.7±0.2 | 65.7±1.1 | 66.6±4.4 |
| AtGS1;3 | 3.9±0.1 | 1210±40 | 850±30 | 162±24 | 93.9±10 | 100.0±0.04 |
| AtGS1;4 | 0.6±0.1 | 48±6 | 400±50 | 79.2±1 | 65.7±1.5 | 73.9±4.2 |
Results for rice (OsGS1;1 and 1;2) and Arabidopsis thaliana (AtGS1;1 to 1;4) were adapted from Ishiyama et al. (2004a) and Ishiyama et al. (2004b), respectively. Purified recombinant enzymes were used for the assay. Kinetic values for the GS synthetic activities were determined by Eadie–Hofstee equations. One katal of enzyme activity is defined as 1 mol of Gln synthesized per second at 30 °C. Data are means ±SE (n=3).
| Isoenzyme | Km | Vmax (nkat mg−1 protein) | ||||
| Glu (mM) | NH4+ (μM) | ATP (μM) | Glu | NH4+ | ATP) | |
| OsGS1;1 | 1.9±0.0 | 27±5 | 450±20 | 190.0±12.3 | 186.3±18.4 | 170.2±15.1 |
| OsGS1;2 | 2.1±0.0 | 73±2 | 530±80 | 97.4±9.0 | 98.1±1.7 | 109.1±14.8 |
| AtGS1;1 | 1.1±0.4 | <10 | 300±20 | 29.3±1.6 | 27.4±0.7 | 21.4±0.4 |
| AtGS1;2 | 3.8±0.2 | 2450±150 | 1100±140 | 65.7±0.2 | 65.7±1.1 | 66.6±4.4 |
| AtGS1;3 | 3.9±0.1 | 1210±40 | 850±30 | 162±24 | 93.9±10 | 100.0±0.04 |
| AtGS1;4 | 0.6±0.1 | 48±6 | 400±50 | 79.2±1 | 65.7±1.5 | 73.9±4.2 |
| Isoenzyme | Km | Vmax (nkat mg−1 protein) | ||||
| Glu (mM) | NH4+ (μM) | ATP (μM) | Glu | NH4+ | ATP) | |
| OsGS1;1 | 1.9±0.0 | 27±5 | 450±20 | 190.0±12.3 | 186.3±18.4 | 170.2±15.1 |
| OsGS1;2 | 2.1±0.0 | 73±2 | 530±80 | 97.4±9.0 | 98.1±1.7 | 109.1±14.8 |
| AtGS1;1 | 1.1±0.4 | <10 | 300±20 | 29.3±1.6 | 27.4±0.7 | 21.4±0.4 |
| AtGS1;2 | 3.8±0.2 | 2450±150 | 1100±140 | 65.7±0.2 | 65.7±1.1 | 66.6±4.4 |
| AtGS1;3 | 3.9±0.1 | 1210±40 | 850±30 | 162±24 | 93.9±10 | 100.0±0.04 |
| AtGS1;4 | 0.6±0.1 | 48±6 | 400±50 | 79.2±1 | 65.7±1.5 | 73.9±4.2 |
Results for rice (OsGS1;1 and 1;2) and Arabidopsis thaliana (AtGS1;1 to 1;4) were adapted from Ishiyama et al. (2004a) and Ishiyama et al. (2004b), respectively. Purified recombinant enzymes were used for the assay. Kinetic values for the GS synthetic activities were determined by Eadie–Hofstee equations. One katal of enzyme activity is defined as 1 mol of Gln synthesized per second at 30 °C. Data are means ±SE (n=3).
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