Conversion of l-Sorbosone to l-Ascorbic Acid by a NADP-Dependent Dehydrogenase in Bean and Spinach Leaf |
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Authors: | Loewus M W Bedgar D L Saito K Loewus F A |
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Institution: | Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340. |
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Abstract: | An NADP-dependent dehydrogenase catalyzing the conversion of l-sorbosone to l-ascorbic acid has been isolated from Phaseolus vulgaris L. and Spinacia oleracea L. and partially purified. It is stable at −20°C for up to 8 months. Molecular masses, as determined by gel filtration, were 21 and 29 kilodaltons for bean and spinach enzymes, respectively. Km for sorbosone were 12 ± 2 and 18 ± 2 millimolar and for NADP+, 0.14 ± 0.05 and 1.2 ± 0.5 millimolar, for bean and spinach, respectively. Lycorine, a purported inhibitor of l-ascorbic acid biosynthesis, had no effect on the reaction. |
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