Two Arabidopsis proteins synthesize acetylated xylan in vitro.
Two Arabidopsis proteins synthesize acetylated xylan in vitro.
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DOI：
10.1111/tpj.12643
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发表时间：
2014-10
期刊：
影响因子：
--
通讯作者：
York WS
中科院分区：
文献类型：
--
作者：
Urbanowicz BR;Peña MJ;Moniz HA;Moremen KW;York WS
木聚糖是继纤维素和几丁质之后地球上第三大最丰富的糖聚合物。作为木材、谷物和饲料的主要成分，这种天然生物聚合物对人类生活产生了深远的影响。这种高度乙酰化的细胞壁多糖是植物细胞壁的重要组成部分，其功能是作为分子支架，为植物提供机械强度和灵活性。损害木聚糖主链合成的突变导致植物由于维管系统中木质部细胞的塌陷而不能正常生长。对这些突变体的表型分析表明，许多蛋白质参与了木聚糖的生物合成。然而，直接负责木聚糖骨架的延伸和乙酰化的酶尚未明确鉴定。在这里，我们提供了直接的生物化学证据表明，两个拟南芥蛋白，不规则木质部10-L（IRX 10-L）和ESKIMO 1/ TRICOME BIREFRINGENCE 29（ESK 1/TBL 29），催化这些各自的过程在体外。通过鉴定难以捉摸的木聚糖合酶和建立ESK 1/TBL 29作为原型植物多糖O-乙酰基转移酶，我们解决了植物细胞壁生物化学中两个长期存在的问题。这些发现揭示了植物用于合成世界生物质主要成分的分子途径中的完整步骤，并扩展了我们生产具有宝贵特性的糖聚合物的工具包。
Xylan is the third most abundant glycopolymer on earth after cellulose and chitin. As a major component of wood, grain and forage, this natural biopolymer has far-reaching impacts on human life. This highly acetylated cell wall polysaccharide is a vital component of the plant cell wall, which functions as a molecular scaffold, providing plants with mechanical strength and flexibility. Mutations that impair synthesis of the xylan backbone give rise to plants that fail to grow normally due to collapsed xylem cells in the vascular system. Phenotypic analysis of these mutants has implicated many proteins in xylan biosynthesis. However, the enzymes directly responsible for elongation and acetylation of the xylan backbone have not been unambiguously identified. Here we provide direct biochemical evidence that two Arabidopsis thaliana proteins, IRREGULAR XYLEM 10-L (IRX10-L) and ESKIMO1/ TRICOME BIREFRINGENCE 29 (ESK1/TBL29), catalyze these respective processes in vitro. By identifying the elusive xylan synthase and establishing ESK1/TBL29 as the archetypal plant polysaccharide O-acetyltransferase, we have resolved two long-standing questions in plant cell wall biochemistry. These findings shed light on integral steps in the molecular pathways utilized by plants to synthesize a major component of the world's biomass and expand our toolkit for producing glycopolymers with valuable properties.
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