State Key Laboratory of Materials-Oriented Chemical Engineering, College of Food Science and Light Industry, Nanjing University of Technology, No. 5 Xinmofan Road, Gulou District, 210009, Nanjing, China.
Appl Microbiol Biotechnol. 2010 Mar;86(1):295-303. doi: 10.1007/s00253-009-2298-8. Epub 2009 Oct 17.
Welan gum is a microbial polysaccharide produced by Alcaligenes sp. CGMCC2428 that has D-glucose, D-glucuronic acid, D-glucose, and L-rhamnose as the main structural unit. The biosynthetic pathway of sugar nucleotides essential for producing welan gum in this strain was established in the following ways: (1) the detection of the presence of several intermediates and key enzymes; (2) the analysis of the response upon addition of precursors to the culture medium; (3) the correlation of the activities between several key enzymes with the yields of welan gum. With addition of 200-microM glucose-6-phosphate and fructose-6-phosphate, the production of welan gum was improved by 18%. The activities of phosphoglucomutase, phosphomannose isomerase, UDP-glucose pyrophosphorylase, and dTDP-glucose pyrophosphorylase, correlated well with the yields of welan gum. According to these findings, the biosynthetic pathway was proposed to involve the metabolism of glucose via two discrete systems. The first involves conversion of glucose to glucose-6-phosphate, with further reactions producing glucose-1-phosphate and fructose-6-phosphate, which are metabolized to the nucleotide sugar precursors of welan gum. The second system involves metabolism of glucose to synthesize the basic structural skeleton of the cell via central metabolic pathways, including the Entner-Doudoroff pathway, the pentose phosphate pathway, and the tricarboxylic acid cycle.
韦兰胶是一种由 Alcaligenes sp. CGMCC2428 产生的微生物多糖，其主要结构单元为 D-葡萄糖、D-葡萄糖醛酸、D-葡萄糖和 L-鼠李糖。该菌株合成韦兰胶所需的糖核苷酸的生物合成途径是通过以下几种方式建立的：（1）检测几种中间产物和关键酶的存在；（2）分析向培养基中添加前体时的反应；（3）几种关键酶的活性与韦兰胶产量之间的相关性。添加 200μM 的葡萄糖-6-磷酸和果糖-6-磷酸后，韦兰胶的产量提高了 18%。磷酸葡糖变位酶、磷酸甘露糖异构酶、UDP-葡萄糖焦磷酸化酶和 dTDP-葡萄糖焦磷酸化酶的活性与韦兰胶的产量密切相关。根据这些发现，提出了该生物合成途径涉及通过两个离散系统代谢葡萄糖。第一个系统涉及将葡萄糖转化为葡萄糖-6-磷酸，进一步的反应产生葡萄糖-1-磷酸和果糖-6-磷酸，这些磷酸化合物被代谢为韦兰胶的核苷酸糖前体。第二个系统涉及通过包括 Entner-Doudoroff 途径、戊糖磷酸途径和三羧酸循环在内的中心代谢途径将葡萄糖代谢合成细胞的基本结构骨架。
