Biosynthesis of pectin, a plant cell wall polysaccharide

果胶（一种植物细胞壁多糖）的生物合成

• 批准号: 12640627
• 负责人: TSUMURAYA Yoichi
• 金额: $ 1.47万
• 依托单位: Saitama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640627/
• 关键词: cell wall; pectin; galactoronic acid; galacturonosyltransferase

Pectins are plant cell wall polysaccharides consisting mainly of contiguous unbranched (1→4)-linked α-galacturonic acid (GalA) residues, and participate in various physiological functions including regulation of cell strength, wall porocity, and intercellular adhesion and communication. A membrane preparation of 7-d-old seedlings from azuki bean (Vigna angularis) contained galacturonosyltransferase (GTase) capable of transferring [^<14>C] GalA from UDP-[^<14>C]GalA into polygalacturonic acid (polyGalA) as an exogenous acceptor. The enzyme was maximally active at pH 6.8-7.5 and 25-35℃ in the presence of 5 mM Mn^<2÷> and 0.5% (w/v) TritonX-100. Acid-soluble low-M_r (average M_r 10,000) polyGalA was a more efficient acceptor substrate than acid-insoluble polymer (M_r 70,000). The apparent Michaelis constants for UDP-GalA and low-M_r polyGalA were 0.11 mM and 0.02 mg/ml, respectively. Various pectins with different degrees of methyl-esterification (DE) were poor acceptors, and the enzyme activity tended to decrease with decreasing DE of the pectins. The transfer products from incubation of the enzyme with UDP-[^<14>C]GalA and the low-M_r polyGalA yielded [^<14>C]GalA_2 as the major product upon digestion with an endopolygalacturonase, confirming the incorporation of GalA into polyGalA through contiguous α-1,4-linkages.

果胶是植物细胞壁多糖，主要由α-半乳糖醛酸（GalA）连接而成，具有调节细胞强度、细胞壁孔隙度、细胞间粘附和通讯等多种生理功能。以赤豆（Vigna angularis）7 d龄幼苗为材料，制备了含有半乳糖醛酸转移酶（GTase）的膜，该酶能<14>将UDP-[^C] GalA<14>转化为聚半乳糖醛酸（polyGalA）作为外源受体。该酶在pH 6.8-7.5和25-35℃、5 mM Mn^（2+）和0.5%（w/v）TritonX-100存在下具有最大活性。酸溶性低分子量聚合物（平均分子量为10，000）是一种比酸不溶性聚合物（分子量为70，000）更有效的受体底物。UDP-GalA和低分子量polyGalA的表观米氏常数分别为0.11mM和0.02mg/ml。不同甲酯化度的果胶均为弱受体，酶活性随甲酯化度的降低而降低。UDP-[^<14>C]GalA和低M_r polyGalA孵育<14>的转移产物在用内切多聚半乳糖醛酸酶消化后产生[^ C]GalA_2作为主要产物，证实GalA通过连续的α-1，4-键并入polyGalA。

项目成果

Y.Takeuchi: "<Invitro>___-biosynthesis of homogalacturonan by a membrane-bound galacturonosyltransterase from epicotyls of azuki bean"Bioscience,Biotechnology,and Biochemistry. 65(7). 1519-1527 (2001)

Y.Takeuchi：“<体外>___-通过来自红豆上胚轴的膜结合半乳糖醛酸转移酶生物合成高半乳糖醛酸”生物科学、生物技术和生物化学。

Y.Takeuchi: "In vitro biosynthesis of homogalacturonan by a membrane-bound galacturonosyltransferase from epilotyls of azuki bean"Bioscience, Biotechnology and Biochemistry. 65, No.7. 1519-1527 (2001)

Y.Takeuchi：“通过膜结合的半乳糖醛酸基转移酶从小豆的表皮中体外生物合成高半乳糖醛酸”生物科学、生物技术和生物化学。

Y.Takeuchi: "In vitro biosynthesis of homogalacturona by a membrane-bound galacturonosyl transferase from epicotyls of azuki bean"Bioscience, Biotechnology, and Biochemistry. 65. 1519-1527 (2001)

Y.Takeuchi：“通过来自小豆上胚轴的膜结合半乳糖醛酸转移酶体外生物合成同型半乳糖醛酸”生物科学、生物技术和生物化学。

T.Takeuchi: "In vitro biosynthesis of homogalacturonan by a membrane-bound galacturonosyltransterase from epilotyls of azuki bean"Bioscience, Biotechnology, and Biochemistry. 65(7). 1519-1527 (2001)

T.Takeuchi：“通过膜结合的半乳糖醛酸基转移酶从小豆的表层体外生物合成高半乳糖醛酸”生物科学、生物技术和生物化学。

Y.Takeuchi: "In vitro biosynthesis of homogalacturonan by a membrane-bound galacturonosyltrans-ferase from epicotyls of azuki bean"Bioscience, Biotechnology, and Biochemistry. (印刷中).

Y. Takeuchi：“通过来自小豆上胚轴的膜结合半乳糖醛酸基转移酶体外生物合成高半乳糖醛酸”生物科学、生物技术和生物化学（正在出版）。