Function of Boron at the interface between cell walls-cell membrane

硼在细胞壁-细胞膜界面的作用

• 批准号: 11660061
• 负责人: MATOH Toru
• 金额: $ 2.3万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11660061/
• 关键词: Boron; Cell wall; Calcium; Pectin methyl esterase; Cultured tobacco cells; Pectic polysaccharide; ラムノガラクツロナンII; 必須元素

We have revealed that the essential plant nutrient element boron (B) works to cross-link pectic polysaccharide chains at the rhamnogalacturonan II (RG-II) sites along the chain. In the cross-link, Ca^<2+> ions are also involved to connect the chains. Ca^<2+> are considered to bind ionically with the carboxyl groups of polygalacturonic acids. Polygalacturonic acids are secreted through Golgi vesicles as in a methyl-esterified form. In cell walls after secretion, the methyl moiety is hydrolyzed with pectin methyl esterase (PME) to prodtuce free carboxylic group. In this study, I have concentrated on the PME of various plant sources.PME enzymes are all localized in cell walls of cultured tobacco cells, pea stems and carrot roots. They are comprised of several isoenzymes. In tobacco cells, nearly all the enzymes are basic in the isoelectric point (IP), on the other hand 70% of the carrot enzymes are neutral in IP.All the PME enzymes need Ca^<2+> for their activities, and the Km values for Ca^<2+> were calculated to be 3 mM.Boron did not activate the enzyme. One of the basic isoenzymes of tobacco is now under purification.

我们已经发现，植物必需的营养元素硼(B)可以使鼠李半乳糖醛酸链(RG-II)上的果胶多糖链发生交联。在交联中，Ca~(2+)~(2+)离子也参与了链的连接。Ca~(2+)~(2+)被认为与聚半乳糖醛酸的羧基离子结合。多聚半乳糖醛酸以甲酯化形式通过高尔基体小泡分泌。在分泌后的细胞壁中，甲基部分被果胶甲酯酶(PME)水解，生成游离的羧基。在这项研究中，我集中研究了各种植物来源的PME。PME酶都定位于培养的烟草细胞、豌豆茎和胡萝卜根的细胞壁中。它们由几种同工酶组成。在烟草细胞中，几乎所有的酶在等电点(IP)处都是碱性的，而胡萝卜酶中70%的酶在IP处是中性的。所有PME酶的活性都需要钙离子，计算出钙离子的Km值为3 mM。烟草的一种基本同工酶目前正在提纯中。

项目成果

Toru Matoh, Miki Takasaki, Masaru Kobayashi, Kenji Takabe: "Boron Nutrition of Cultured Tobacco BY-2 Cells.III. Characterization of the Boron-Rhamnogalacturonan II Complex in Cells Acclimated to Low Levels of Boron"Plant Cell Physiology. 41(3)(印刷中). (2000

Toru Matoh、Miki Takasaki、Masaru Kobayashi、Kenji Takabe：“培养的烟草 BY-2 细胞的硼营养。III. 适应低水平硼的细胞中硼-鼠李糖半乳糖醛酸 II 复合物的表征”植物细胞生理学 41(3)。 （出版中）。