Gerstmeir Robert, Wendisch Volker F, Schnicke Stephanie, Ruan Hong, Farwick Mike, Reinscheid Dieter, Eikmanns Bernhard J
Department of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
J Biotechnol. 2003 Sep 4;104(1-3):99-122. doi: 10.1016/s0168-1656(03)00167-6.
The amino acid producing Corynebacterium glutamicum grows aerobically on a variety of carbohydrates and organic acids as single or combined sources of carbon and energy. Among the substrates metabolized are glucose and acetate which both can also serve as substrates for amino acid production. Based on biochemical, genetic and regulatory studies and on quantitative determination of metabolic fluxes during utilization of acetate and/or glucose, this review summarizes the present knowledge on the different steps of the fundamental pathways of acetate utilization in C. glutamicum, namely, on acetate transport, acetate activation, tricarboxylic acid (TCA) cycle, glyoxylate cycle and gluconeogenesis. It becomes evident that, although the pathways of acetate utilization follow the same theme in many bacteria, important biochemical, genetic and regulatory peculiarities exist in C. glutamicum. Recent genome wide and comparative expression analyses in C. glutamicum cells grown on glucose and on acetate substantiated previously identified transcriptional regulation of acetate activating enzymes and of glyoxylate cycle enzymes. Additionally, a variety of genes obviously also under transcriptional control in response to the presence or absence of acetate in the growth medium were uncovered. These genes, thus also belonging to the acetate stimulon of C. glutamicum, include genes coding for TCA cycle enzymes (e.g. aconitase and succinate dehydrogenase), for gluconeogenesis (phosphoenolpyruvate carboxykinase), for glycolysis (pyruvate dehydrogenase E1) and genes coding for proteins with hitherto unknown function. Although the basic mechanism of transcriptional regulation of the enzymes involved in acetate metabolism is not yet understood, some recent findings led to a better understanding of the adaptation of C. glutamicum to acetate at the molecular level.
产氨基酸的谷氨酸棒杆菌在多种碳水化合物和有机酸上进行有氧生长，这些物质可作为单一或组合的碳源和能源。在其代谢的底物中包括葡萄糖和乙酸盐，这两者也都可作为氨基酸生产的底物。基于生化、遗传和调控研究以及对乙酸盐和/或葡萄糖利用过程中代谢通量的定量测定，本综述总结了目前关于谷氨酸棒杆菌中乙酸盐利用基本途径不同步骤的知识，即乙酸盐转运、乙酸盐活化、三羧酸（TCA）循环、乙醛酸循环和糖异生。显而易见，尽管乙酸盐利用途径在许多细菌中遵循相同的模式，但谷氨酸棒杆菌中存在重要的生化、遗传和调控特性。最近在以葡萄糖和乙酸盐为生长底物的谷氨酸棒杆菌细胞中进行的全基因组和比较表达分析，证实了先前鉴定的乙酸盐活化酶和乙醛酸循环酶的转录调控。此外，还发现了多种明显受生长培养基中乙酸盐存在与否转录调控的基因。因此，这些基因也属于谷氨酸棒杆菌的乙酸盐刺激子，包括编码TCA循环酶（如乌头酸酶和琥珀酸脱氢酶）、糖异生（磷酸烯醇式丙酮酸羧激酶）、糖酵解（丙酮酸脱氢酶E1）的基因以及编码功能未知蛋白质的基因。尽管参与乙酸盐代谢的酶的转录调控基本机制尚不清楚，但一些最新发现使我们对谷氨酸棒杆菌在分子水平上对乙酸盐的适应性有了更好的理解。
