title: Engineering of a sialic acid synthesis pathway in transgenic plants by expression of bacterial Neu5Ac-synthesizing enzymes.
abstract: Plants are a low-cost and contamination-free factory for the production of recombinant pharmaceutical proteins. However, plant-made pharmaceuticals differ from their mammalian homologues by the structure of their N-linked glycans. For instance, most mammalian glycoproteins harbour terminal sialic acids that control their half-life in the bloodstream. The absence of the whole sialylation machinery in plants is of major concern as non-sialylated plant-made pharmaceuticals may not perform at their full potential in humans, because of their removal from the circulation through the involvement of hepatic cell receptors. In this context, we have investigated the synthesis of N-acetylneuraminic acid (Neu5Ac) in the cytosol of plants by either the re-routing of the endogenous 3-deoxy-d-manno-2-octulosonic acid (Kdo) biosynthetic pathway or the expression of microbial Neu5Ac-synthesizing enzymes. In this paper, we demonstrate that the plant Kdo-8P synthase is not able to use N-acetyl d-mannosamine as a substrate, and thus re-routing of the Kdo pathway for the synthesis of Neu5Ac is not possible. Consequently, we expressed genes encoding Neu5Ac lyase from Escherichia coli and Neu5Ac synthase (neuB2) from Campylobacter jejuni in plants. These resulted in the production of functional enzymes in the cytosol, which in turn can catalyse the synthesis of Neu5Ac in vitro. Experiments were carried out on two models, Bright Yellow 2 (BY2) tobacco cells and Medicago sativa (alfalfa), the perennial legume crop.
authors.affiliation: CNRS-UMR 6037, GDR2590, IFRMP 23, Université de Rouen, 76821 Mont Saint Aignan Cédex, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Paccalet
authors.forename: Muriel
authors.initials: M
authors.lastname: Bardor
authors.forename: Christophe
authors.initials: C
authors.lastname: Rihouey
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delmas
authors.forename: Christian
authors.initials: C
authors.lastname: Chevalier
authors.forename: Marc-André
authors.initials: MA
authors.lastname: D'Aoust
authors.forename: Loïc
authors.initials: L
authors.lastname: Faye
authors.forename: Louis
authors.initials: L
authors.lastname: Vézina
authors.forename: Véronique
authors.initials: V
authors.lastname: Gomord
authors.forename: Patrice
authors.initials: P
authors.lastname: Lerouge
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D016123:Campylobacter jejuni / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D007652:Oxo-Acid-Lyases / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; C018730:N-acetylneuraminate synthase; D007652:Oxo-Acid-Lyases