Regulation of C4 photosynthesis: characterization of a protein factor mediating the activation and inactivation of NADP-malate dehydrogenase. |
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Authors: | T Kagawa M D Hatch |
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Institution: | Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Post Office Box 1600, Canberra City, A.C.T., Australia 2601 |
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Abstract: | The leaf NADP-malate dehydrogenase of Zea mays is rapidly activated when leaves are illuminated and inactivated in the dark. The present studies show that inactive enzyme isolated from darkened leaves was activated by dithiothreitol and that the active enzyme was rapidly inactivated by oxygen in dithiothreitol-free solutions. Following the fractionation of leaf extracts, both the activation and inactivation of NADP-malate dehydrogenase in vitro were partially or totally dependent upon a separate small molecular weight protein factor. Activation and inactivation were largely or solely dependent upon this factor at pH 8.0 or less, but apparently only partially factor dependent at pH 9.0. The factor was heat stable, inactivated by incubation with trypsin, and had a molecular weight of about 10,000. It was mostly associated with the chloroplasts of mesophyll cells. |
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Keywords: | Recipient of Research Career Development Award 1 K04 00036 from the United States Public Health Service National Institutes of Health author to whom all correspondence should be addressed |
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