Water stress induced alterations in ornithine aminotransferase of ragi (Eleusine coracana): Protection by proline against heat inactivation and denaturation by urea and guanidinium chloride |
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Authors: | Rajendra P Kandpal N Appaji Rao |
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Institution: | (1) Department of Biochemistry, Indian Institute of Science, 560012 Bangalore, India;(2) Present address: Molecular Biology Institute, University of California, 90024 Los Angeles, California, USA |
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Abstract: | Water stress resulted in a specific response leading to a large and significant increase (80-fold) in free proline content
of ragi (Eleusine coracana leaves and seedlings. L-Proline protected ornithine aminotransferase, an enzyme in the pathway for proline biosynthesis,
isolated from normal and stressed ragi leaves against heat inactivation and denaturation by urea and guanidinium chloride.
The protection of the stressed enzyme by L-proline was much more complete than that of the enzyme isolated from normal leaves.
While L-ornithine, one of the substrates, protected the stressed enzyme against inactivation, it enhanced the rate of inactivation
of the normal enzyme. α-Ketoglutarate protected both the normal and stressed enzyme against inactivation and denaturation.
These results support the suggestion that ornithine aminotransferase has undergone a structural alteration during water stress.
In view of the causal relationship between elevated temperature and water stress of plants under natural conditions, the protection
afforded by proline against inactivation and denaturation of the enzyme from stressed leaves assumes significance. These results
provide an explanation for a possible functional importance of proline accumulation during water stress. |
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Keywords: | Ornithine aminotransferase proline water stress Eleusine coracana |
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