Effect of glucose on poly-γ-glutamic acid metabolism in Bacillus licheniformis.
Effect of glucose on poly-γ-glutamic acid metabolism in Bacillus licheniformis.
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葡萄糖对地衣芽孢杆菌多聚γ-谷氨酸代谢的影响
DOI：
10.1186/s12934-017-0642-8
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发表时间：
2017-02-08
影响因子：
6.4
通讯作者：
He N
中科院分区：
文献类型：
--
作者：
Yu W;Chen Z;Ye H;Liu P;Li Z;Wang Y;Li Q;Yan S;Zhong CJ;He N
聚γ-谷氨酸（γ-PGA）是一种很有前途的高分子，具有替代化学合成聚合物的潜力。γ-PGA可以由许多微生物产生，包括芽孢杆菌。地衣芽孢杆菌CGMCC2876以甘油和柠檬酸三钠为最优碳源时分泌γ-PGA，以葡萄糖为唯一碳源时分泌多糖。为了更好地了解聚合物物质分泌的代谢机制，我们应用SWATH在蛋白质组水平上研究了葡萄糖对多糖和γ-PGA产生的影响。葡萄糖浓度为5 g/L和10 g/L时，γ-PGA浓度分别降低了31.54%和61.62%，而多糖浓度则从5.2%增加到43.47%。利用SWATH获取LC-MS /MS方法鉴定了在γ-PGA和多糖合成中起相关作用的几个蛋白。CcpA和CcpN共同促进糖酵解，抑制碳通量进入TCA循环，从而减缓谷氨酸合成。另一方面，CcpN切断了甘油代谢的碳通量，进一步减少了γ-PGA的产生。当葡萄糖存在时，CcpA激活了一系列操纵子（glm和epsA-O），将碳通量重新分配到多糖合成中。γ-PGA的产生受NrgB的影响，NrgB在NH4 +和谷氨酸之间转换主要的氮代谢通量。本文首次提出了地衣芽孢杆菌调控两种大分子的机制。这些遗传信息将有助于细菌的工程设计，为各种用途的γ-PGA和多糖的发酵提供可行的策略。本文的在线版本（doi:10.1186/s12934-017-0642-8）包含补充材料，可供授权用户使用。
Poly-gamma-glutamic acid (γ-PGA) is a promising macromolecule with potential as a replacement for chemosynthetic polymers. γ-PGA can be produced by many microorganisms, including Bacillus species. Bacillus licheniformis CGMCC2876 secretes γ-PGA when using glycerol and trisodium citrate as its optimal carbon sources and secretes polysaccharides when using glucose as the sole carbon source. To better understand the metabolic mechanism underlying the secretion of polymeric substances, SWATH was applied to investigate the effect of glucose on the production of polysaccharides and γ-PGA at the proteome level. The addition of glucose at 5 or 10 g/L of glucose decreased the γ-PGA concentration by 31.54 or 61.62%, respectively, whereas the polysaccharide concentration increased from 5.2 to 43.47%. Several proteins playing related roles in γ-PGA and polysaccharide synthesis were identified using the SWATH acquisition LC–MS/MS method. CcpA and CcpN co-enhanced glycolysis and suppressed carbon flux into the TCA cycle, consequently slowing glutamic acid synthesis. On the other hand, CcpN cut off the carbon flux from glycerol metabolism and further reduced γ-PGA production. CcpA activated a series of operons (glm and epsA-O) to reallocate the carbon flux to polysaccharide synthesis when glucose was present. The production of γ-PGA was influenced by NrgB, which converted the major nitrogen metabolic flux between NH4 + and glutamate. The mechanism by which B. licheniformis regulates two macromolecules was proposed for the first time in this paper. This genetic information will facilitate the engineering of bacteria for practicable strategies for the fermentation of γ-PGA and polysaccharides for diverse applications. The online version of this article (doi:10.1186/s12934-017-0642-8) contains supplementary material, which is available to authorized users.