Pectins from citrus peel cell walls contain homogalacturonans homogenous with respect to molar mass, rhamnogalacturonan I and rhamnogalacturonan II
Pectins from citrus peel cell walls contain homogalacturonans homogenous with respect to molar mass, rhamnogalacturonan I and rhamnogalacturonan II
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DOI：
10.1016/j.carbpol.2006.12.024
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发表时间：
2007-06
影响因子：
11.2
通讯作者：
B. M. Yapo;P. Lerouge;J. Thibault;M. Ralet
中科院分区：
文献类型：
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作者：
B. M. Yapo;P. Lerouge;J. Thibault;M. Ralet
采用水、草酸、热稀盐酸和冷稀氢氧化钠从柑桔皮中提取不同结构的果胶。以果胶为原料，经脱酯化后，经弱酸水解得到高半乳糖醛酸聚糖。对它们的大分子性质的研究表明，它们具有相似的数均和重均聚合度，在81-117个半乳糖醛酸单位的范围内，与初始果胶无关。据推测，柑橘皮果胶包括HG的拉伸长度相似的模式，无论提取。采用内切-1，4-α-聚半乳糖醛酸酶，然后通过阴离子交换和分子排阻色谱法，从草酸和酸提取的果胶中分离出鼠李糖半乳糖醛酸聚糖I（RG I）和鼠李糖半乳糖醛酸聚糖II（RG II）。RG I主要由阿拉伯糖、半乳糖、半乳糖醛酸和鼠李糖组成，表明存在阿拉伯聚糖和/或（阿拉伯）半乳聚糖侧链。将酸提果胶所得的RG I分别用内切-1，5-α-l-阿拉伯聚糖酶、内切-1，4-β-d-半乳聚糖酶、α-l-阿拉伯呋喃糖苷酶和β-d-半乳糖苷酶处理，得到脱支RG I（dRG I）。RGs I和dRG I的半乳糖醛酸与鼠李糖的摩尔比非常接近1/1，表明主链中严格重复的[GalA-Rha] n模式。它的结论是，柑橘果胶主要由HG，与几个RG I和一个小RG II馏分。
Pectins of different structures were extracted from citrus peels with water, oxalate, hot dilute hydrochloric acid and cold dilute sodium hydroxide. Homogalacturonans (HGs) were isolated from the four pectins by mild acid hydrolysis after deesterification. The study of their macromolecular properties revealed that they have similar number- and weight-average degrees of polymerisation, in the range of 81–117 galacturonic acid units, irrespective of the initial pectin. It was inferred that citrus peel pectins consist of HG strectches of similar lengths whatever the mode of extraction. Rhamnogalacturonan I (RG I) and rhamnogalacturonan II (RG II) were isolated from the oxalate- and the acid-extracted pectins using an endo-1,4-α-polygalacturonase followed by anion-exchange and size-exclusion chromatographies. RG I was composed mainly of arabinose, galactose, galacturonic acid and rhamnose, suggesting the presence of arabinan and/or (arabino)galactan side chains. Debranched RG I (dRG I) was obtained by treating the RG I arising from acid-extracted pectin with endo-1,5-α-l-arabinanase, endo-1,4-β-d-galactanase, α-l-arabinofuranosidase and β-d-galactosidase in admixture. The molar ratios of galacturonic acid to rhamnose of RGs I and dRG I were very close to 1/1, indicating a strict repeating [GalA–Rha]npattern in the backbone. It is concluded that citrus pectins consist predominantly of HG, with a few RG I and a minor RG II fraction.