The biosynthesis of cyclic carotenes |
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Authors: | R J H Williams G Britton and T W Goodwin |
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Institution: | Department of Biochemistry and Agricultural Biochemistry, University College of Wales, Aberystwyth |
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Abstract: | 1. The incorporation of (3RS)-2-(14)C,(4R)-4-(3)H(1)]mevalonic acid into various cyclic carotenes in the fruit of the tomato mutant delta has been studied. The results confirm our previous view that the alpha-ionone ring of alpha-carotene does not arise by isomerization of a beta-ionone residue, and show that the same is also true for the alpha-ionone ring of delta- and in-carotene and alpha-zeacarotene. 2. The incorporation of (3RS)-2-(14)C,2-(3)H(2)]mevalonic acid into alpha- and beta-carotene in carrot roots has been studied. The results show that the beta-ionone ring of beta-carotene does not arise by isomerization of the alpha-ionone residue of alpha-carotene. 3. These experiments show that alpha- and beta-ionone rings in cyclic carotenes are formed independently, probably by elimination of different protons from the same carbonium ion intermediates. |
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