Abstract
With intact spinach (Spinacia oleracea L. cv. Vital R) chloroplasts, the activity of the NADP-dependent malate dehydrogenase after activation by light was 30 micromoles of malate formed per milligram of chlorophyll per hour; an identical rate of O2 evolution was obtained upon oxaloacetate reduction by the intact plastids. However, when the activity of NADP-dependent malate dehydrogenase was measured subsequently to maximal activation of the enzyme by dithiothreitol (DTT) an average rate of 113 micromoles per milligram of chlorophyll per hour was obtained. When membranes and stroma were separated after osmotic disruption of the chloroplasts, 28% of NADP-dependent malate dehydrogenase activity inducible by DTT was found with the membranes and 72% was found in the stromal fraction. The membrane-associated portion of the enzyme corresponds well with the activity achieved after activation by light. About 64% of an activator system was found to be associated also with the membrane fraction. Washing the membranes with buffer removed more activator than enzyme. However, both were removed almost completely by ethylenediaminetetraacetate. It was concluded that both a portion of the enzyme and the total activator system are associated with the chloroplast membranes in vivo and that the activator is more loosely bound than the enzyme. A model describing the partial activation of chloroplastic NADP-dependent malate dehydrogenase by light and the total activation by DTT is presented.
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Selected References
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- Anderson L. E., Avron M. Light Modulation of Enzyme Activity in Chloroplasts: Generation of Membrane-bound Vicinal-Dithiol Groups by Photosynthetic Electron Transport. Plant Physiol. 1976 Feb;57(2):209–213. doi: 10.1104/pp.57.2.209. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Anderson L. E., Nehrlich S. C., Champigny M. L. Light modulation of enzyme activity: activation of the light effect mediators by reduction and modulation of enzyme activity by thiol-disulfide exchange. Plant Physiol. 1978 Apr;61(4):601–605. doi: 10.1104/pp.61.4.601. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Beck E., Stransky H., Fürbringer M. Synthesis of hamamelose-diphosphate by isolated spinach chloroplasts. FEBS Lett. 1971 Mar 16;13(4):229–234. doi: 10.1016/0014-5793(71)80542-2. [DOI] [PubMed] [Google Scholar]
- Gupta V. K., Anderson L. E. Light modulation of the activity of carbon metabolism enzymes in the crassulacean Acid metabolism plant kalanchoë. Plant Physiol. 1978 Mar;61(3):469–471. doi: 10.1104/pp.61.3.469. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jacquot J. P., Vidal J., Gadal P. Identification of a protein factor involved in dithiothreitol activation of NADP malate dehydrogenase from French bean leaves. FEBS Lett. 1976 Dec 1;71(2):223–227. doi: 10.1016/0014-5793(76)80937-4. [DOI] [PubMed] [Google Scholar]
- Jensen R. G., Bassham J. A. Photosynthesis by isolated chloroplasts. Proc Natl Acad Sci U S A. 1966 Oct;56(4):1095–1101. doi: 10.1073/pnas.56.4.1095. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Johnson H. S. NADP-malate dehydrogenase: photoactivation in leaves of plants with Calvin cycle photosynthesis. Biochem Biophys Res Commun. 1971 May 21;43(4):703–709. doi: 10.1016/0006-291x(71)90672-3. [DOI] [PubMed] [Google Scholar]
- Kagawa T., Hatch M. D. Regulation of C4 photosynthesis: characterization of a protein factor mediating the activation and inactivation of NADP-malate dehydrogenase. Arch Biochem Biophys. 1977 Nov;184(1):290–297. doi: 10.1016/0003-9861(77)90353-8. [DOI] [PubMed] [Google Scholar]
- Ting I. P., Rocha V. NADP-specific malate dehydrogenase of green spinach leaf tissue. Arch Biochem Biophys. 1971 Nov;147(1):156–164. doi: 10.1016/0003-9861(71)90322-5. [DOI] [PubMed] [Google Scholar]