ENZYME CATALYSIS AND REGULATION
1-Deoxy-d-xylulose-5-phosphate Synthase, a Limiting Enzyme for Plastidic Isoprenoid Biosynthesis in Plants*

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The initial step of the plastidic 2C-methyl-d-erythritol 4-phosphate (MEP) pathway that produces isopentenyl diphosphate is catalyzed by 1-deoxy-d-xylulose-5-phosphate synthase. To investigate whether or not 1-deoxy-d-xylulose-5-phosphate synthase catalyzes a limiting step in the MEP pathway in plants, we produced transgenic Arabidopsis plants that over- or underexpress this enzyme. Compared with non-transgenic wild-type plants, the transgenic plants accumulate different levels of various isoprenoids such as chlorophylls, tocopherols, carotenoids, abscisic acid, and gibberellins. Phenotypically, the transgenic plants had slight alterations in growth and germination rates. Because the levels of several plastidic isoprenoids correlate with changes in 1-deoxy-d-xylulose-5-phosphate synthase levels, we conclude that this enzyme catalyzes one of the rate-limiting steps of the MEP biosynthetic pathway. Furthermore, since the product of the MEP pathway is isopentenyl diphosphate, our results suggest that in plastids the pool of isopentenyl diphosphate is limiting to isprenoid production.

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Published, JBC Papers in Press, March 22, 2001, DOI 10.1074/jbc.M100854200

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This research was supported by Consejo Nacional de Ciencia y Tecnologı́a Grant 31791-N, Dı́rección General de Asuntos del Personal Academico Grant IN205697, and by BASF.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Fellow from Consejo Nacional de Ciencia y Tecnologı́a.