Light activation of NADP malic enzyme in leaves of maize : marginal increase in activity, but marked change in regulatory properties of enzyme
This article reports the characteristics of light activation of NADP-malic enzyme (NADP-ME, EC 1.1.1.40) in leaf discs of maize (Zea mays cv. VMH 404) for the first time. The leaf discs were illuminated in the presence of 2 mmol/L bicarbonate, as light activation increases in the presence of bicarbo...
| Veröffentlicht in: | Journal of plant physiology. - 1979. - 160(2003), 1 vom: 15. Jan., Seite 51-6 |
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| Weitere Verfasser: | , |
| Format: | Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2003
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| Zugriff auf das übergeordnete Werk: | Journal of plant physiology |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Malate Dehydrogenase EC 1.1.1.37 malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) EC 1.1.1.40 |
| Zusammenfassung: | This article reports the characteristics of light activation of NADP-malic enzyme (NADP-ME, EC 1.1.1.40) in leaf discs of maize (Zea mays cv. VMH 404) for the first time. The leaf discs were illuminated in the presence of 2 mmol/L bicarbonate, as light activation increases in the presence of bicarbonate. Upon illumination, the Vmax of NADP-ME increased by about 30%. Although small, the increase was consistent and significant. The changes in regulatory properties of NADP-ME were quite pronounced. The extent of light activation was similar when substrate (malate) concentration was either 4 mmol/L (saturating) or 0.01 mmol/L (limiting). There was only a marginal change in the Km for malate, but there was marked change in the response of NADP-ME to activators or inhibitors. The Ki for pyruvate and oxalate increased by 100 and 67% respectively, while the Ka for the citrate and succinate increased by 36 and 32% respectively. These results suggest that the NADP-ME becomes less sensitive to feedback inhibition on illumination. The light-induced change seems to be due, at least partially, to the reduction of dithiols, as incubation of leaf extracts with DTE dampened light activation of NADP-ME. We conclude that the properties of NADP-ME do change on illumination. Although there was only a marginal increase in the activity of the enzyme on illumination of leaf discs, the changes in regulatory properties of NADP-ME were marked |
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| Beschreibung: | Date Completed 27.05.2003 Date Revised 30.09.2020 published: Print Citation Status MEDLINE |
| ISSN: | 1618-1328 |