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Construction of a Functional CMP-Sialic Acid Biosynthesis Pathway in Arabidopsis

Alexandra Castilho, Martin Pabst, Renaud Leonard, Christiane Veit, Friedrich Altmann, Lukas Mach, Josef Glössl, Richard Strasser and Herta Steinkellner
Plant Physiology
Vol. 147, No. 1 (May, 2008), pp. 331-339
Stable URL: http://www.jstor.org/stable/40066029
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Construction of a Functional CMP-Sialic Acid Biosynthesis Pathway in Arabidopsis
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Abstract

Previous studies have reported that plants contain negligible amounts of free or protein-bound N-acetylneuraminic acid (Neu5Ac). This is a major disadvantage for the use of plants as a biopharmaceutical expression system, since N-glycans with terminal Neu5Ac residues are important for the biological activities and half-lives of recombinant therapeutic glycoproteins in humans. For the synthesis of Neu5Ac-containing N-glycans, plants have to acquire the ability to synthesize Neu5Ac and its nucleotide-activated derivative, cytidine monophospho-N-acetylneuraminic acid. In this study, we have generated transgenic Arabidopsis (Arabidopsis thaliana) plants expressing three key enzymes of the mammalian Neu5Ac biosynthesis pathway: UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, N-acetylneuraminic acid phosphate synthase, and CMP-N-acetylneuraminic acid synthetase. Simultaneous expression of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase and N-acetylneuraminic acid phosphate synthase resulted in the generation of significant Neu5Ac amounts (1,275 nmol g⁻¹ fresh weight in leaves) in planta, which could be further converted to cytidine monophospho-N-acetylneuraminic acid (2.4 nmol g⁻¹ fresh weight in leaves) by coexpression of CMP-N-acetylneuraminic acid synthetase. These findings are a major step toward the production of Neu5Ac-containing glycoproteins in plants.

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