Delmas Frédéric, Petit Johann, Joubès Jérôme, Séveno Martial, Paccalet Thomas, Hernould Michel, Lerouge Patrice, Mouras Armand, Chevalier Christian
Unité Mixte de Recherche 619 de Physiologie et Biotechnologie Végétales, Institut de Biologie Végétale Moléculaire, Centre de Recherche Institut National de la Recherche Agronomique-Bordeaux, boite postale 81, 33883 Villenave d'Ornon cedex, France.
Plant Physiol. 2003 Sep;133(1):348-60. doi: 10.1104/pp.103.026872.
3-deoxy-D-manno-2-octulosonic acid-8-phosphate (Kdo-8-P) synthase catalyzes the condensation of phosphoenolpyruvate with D-arabinose-5-phosphate to yield Kdo-8-P. Kdo-8-P is the phosphorylated precursor of Kdo, a rare sugar only found in the rhamnogalacturonan II pectic fraction of the primary cell walls of higher plants and of cell wall polysaccharides of some green algae. A cDNA named LekdsA (accession no. AJ294902) encoding tomato (Lycopersicon esculentum) Kdo-8-P synthase has been isolated. The recombinant protein rescued a kdsA thermosensitive mutant of Salmonella typhimurium impaired in the synthesis of a functional Kdo-8-P synthase. Using site-directed mutagenesis of LekdsA cDNA, the tomato Kdo-8-P synthase was shown to possess the same essential amino acids that form the active sites in the bacterial enzymes. The tomato kdsA gene expression and the relevant Kdo-8-P synthase activity were preferentially associated to dividing cells, in the course of the early development of tomato fruit and in meristematic tissues. Furthermore, the transcription of the kdsA gene was found to oscillate during the cell cycle in tobacco (Nicotiana tabacum) Bright-Yellow 2 synchronized cells with a maximum during mitosis.
3-脱氧-D-甘露-2-辛酮糖酸-8-磷酸（Kdo-8-P）合酶催化磷酸烯醇丙酮酸与D-阿拉伯糖-5-磷酸缩合生成Kdo-8-P。Kdo-8-P是Kdo的磷酸化前体，Kdo是一种稀有糖，仅存在于高等植物初生细胞壁的鼠李半乳糖醛酸聚糖II果胶部分以及一些绿藻的细胞壁多糖中。已分离出一个名为LekdsA（登录号AJ294902）的cDNA，其编码番茄（Lycopersicon esculentum）的Kdo-8-P合酶。该重组蛋白挽救了鼠伤寒沙门氏菌中一个在功能性Kdo-8-P合酶合成方面受损的kdsA温度敏感突变体。通过对LekdsA cDNA进行定点诱变，发现番茄Kdo-8-P合酶具有与细菌酶中形成活性位点相同的必需氨基酸。在番茄果实早期发育过程中和分生组织中，番茄kdsA基因表达及相关的Kdo-8-P合酶活性优先与分裂细胞相关。此外，发现在烟草（Nicotiana tabacum）Bright-Yellow 2同步化细胞的细胞周期中，kdsA基因的转录会发生振荡，在有丝分裂期间达到最大值。
