Uronic acid-containing oligosaccharins: Their biosynthesis, degradation and signalling roles in non-diseased plant tissues
Uronic acid-containing oligosaccharins: Their biosynthesis, degradation and signalling roles in non-diseased plant tissues
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DOI：
10.1016/s0981-9428(00)00163-7
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发表时间：
2000-01-01
影响因子：
6.5
通讯作者：
Fry, SC
中科院分区：
文献类型：
--
作者：
Dumville, JC;Fry, SC
由微生物酶产生的果胶低聚糖是众所周知的寡糖素，在患病植物中引发防御反应。还提出了在非病害植物中的调节作用：例如，通过果胶水解在体外产生的寡糖促进番茄（Lycopersicon esculentum L.）和其他水果。内聚半乳糖醛酸酶（endo-PG; EC 3.2.1.15）存在于许多水果中，理论上可以产生这种寡糖。然而，仅仅酶的出现并不能证明它起作用;必须在体内寻找拟议的产物（寡糖）。最近的证据表明，水果组织自然产生果胶低聚糖，其中一些添加到未成熟的水果时促进成熟。这些研究，补充了早期的工作，在体外产生的寡糖，提供了一种手段，发现新的寡糖。与果实不同，玫瑰（Rosa sp.）不产生果胶低聚糖。它们的“缺失”不是由于过快的周转：当加入[C-14]-寡聚半乳糖醛酸时，它们只经历缓慢的水解。通过外切多聚半乳糖醛酸酶（exo-PG; EC 3.2.1.67）进行水解，产生游离半乳糖醛酸（GalA）。如果不添加寡聚半乳糖醛酸，则培养基中不会积累GalA;因此，外切-PG在健康的玫瑰细胞中通常不起作用。外切-PG大概是"储备“，可用于修剪由植物病原体产生的寡聚半乳糖醛酸。我们的结论是，在体内的壁酶的作用是最好的研究在体内的碳水化合物代谢的水平，而不是通过测定提取的酶在体外。由玫瑰细胞培养物产生的主要含糖醛酸寡糖是α-D-吡喃甘露糖基-（1->4）-α-D-吡喃葡萄糖醛酸基-（1->2）-肌醇，其可能是与介导胰岛素作用的肌醇磷酸聚糖相关的新型植物糖脂衍生寡糖素。(C)2000年，Elsevier SAS科学与医学版。
Pectic oligosaccharides, produced by microbial enzymes, are well-known oligosaccharins, eliciting defence responses in diseased plants. Regulatory roles in non-diseased plants have also been proposed: e.g. oligosaccharides, generated in vitro by hydrolysis of pectins, promote ripening in tomato (Lycopersicon esculentum L.) and other fruits. Endopolygalacturonase (endo-PG; EC 3.2.1.15) occurs in many fruits and theoretically could generate such oligosaccharides. However, the mere occurrence of an enzyme does not prove that it acts; the proposed products (oligosaccharides) must be sought in vivo. Recent evidence indicates that fruit tissues do naturally produce pectic oligosaccharides, some of which promote ripening when added to unripe fruits. Such studies, complementing earlier work on in-vitro generated oligosaccharides, provide a means of discovering novel oligosaccharins. Unlike fruits, cell cultures of rose (Rosa sp.) produce no pectic oligosaccharides. Their 'absence' is not due to excessively rapid turnover: when [C-14]-oligogalacturonides are added, they undergo only slow hydrolysis. The hydrolysis is by exo-polygalacturonases (exo-PG; EC 3.2.1.67), yielding free galacturonic acid (GalA). If no oligogalacturonides are added, no GalA accumulates in the medium; therefore, exo-PG does not normally operate in healthy rose cells. Exo-PG is presumably 'in reserve', available to trim oligogalacturonides made by phytopathogens. We conclude that the in-vivo action of a wall enzyme is best studied at the level of carbohydrate metabolism in vivo rather than by assay of extracted enzymes in vitro. The major uronic acid-containing oligosaccharide produced by rose cell cultures is alpha-D-mannopyranosyl-(1-->4)-alpha-D-glucuronopyranosyl-(1-->2)-myo-inositol, which may be a novel phytoglycolipid-derived oligosaccharin related to the inositolphosphoglycans that mediate insulin action. (C) 2000 Editions scientifiques et medicales Elsevier SAS.