Regulation of acetate metabolism in Corynebacterium glutamicum: transcriptional control of the isocitrate lyase and malate synthase genes
Regulation of acetate metabolism in Corynebacterium glutamicum: transcriptional control of the isocitrate lyase and malate synthase genes
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DOI：
10.1007/s002030050497
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发表时间：
1997-10-01
影响因子：
2.8
通讯作者：
Eikmanns, BJ
中科院分区：
文献类型：
--
作者：
Wendisch, VF;Spies, M;Eikmanns, BJ
在产氨基酸微生物谷氨酸棒杆菌中，当细胞在乙酸盐上生长时，乙酸激活酶（乙酸激酶和磷酸转乙酰酶）以及乙醛酸循环酶（异柠檬酸裂解酶和苹果酸合酶）的比活性较高（分别为每毫克蛋白质0.8、2.9、2.1和1.8单位）。当细胞在葡萄糖或其他碳源（如乳酸盐、琥珀酸盐或谷氨酸盐）上生长时，比活性分别降低了2到4倍（乙酸激酶和磷酸转乙酰酶）以及45到100倍（异柠檬酸裂解酶和苹果酸合酶），这表明这四种酶的合成受生长培养基中的乙酸盐调控。对谷氨酸棒杆菌异柠檬酸裂解酶和苹果酸合酶基因（aceA和aceB）进行的比较性Northern（RNA）分析以及转录融合实验表明，aceA和aceB分别作为1.6 kb和2.7 kb的单顺反子转录本进行转录，并且异柠檬酸裂解酶和苹果酸合酶合成的调控是在各自启动子的转录水平上进行的。令人惊讶的是，乙酸激酶或磷酸转乙酰酶有缺陷的谷氨酸棒杆菌突变体，无论培养基中是否存在乙酸盐，其他三种酶（磷酸转乙酰酶、异柠檬酸裂解酶和苹果酸合酶，或者乙酸激酶、异柠檬酸裂解酶和苹果酸合酶）的比活性都较低。这一结果以及细胞内高浓度的乙酰辅酶A与异柠檬酸裂解酶、苹果酸合酶、乙酸激酶和磷酸转乙酰酶的高比活性之间的相关性表明，乙酰辅酶A或其衍生物可能是谷氨酸棒杆菌乙酸代谢相关酶基因调控的生理触发因素。
In the amino-acid-producing microorganism Corynebacterium glutamicum, the specific activities of the acetate-activating enzymes acetate kinase and phosphotransacetylase and those of the glyoxylate cycle enzymes isocitrate lyase and malate synthase were found to be high when the cells were grown on acetate (0.8, 2.9, 2.1, and 1.8 U/mg protein, respectively). When the cells were grown on glucose or on other carbon sources such as lactate, succinate, or glutamate, the specific activities were two-to fourfold (acetate kinase and phosphotransacetylase) and 45- to 100-fold (isocitrate lyase and malate synthase) lower, indicating that the synthesis of the four enzymes is regulated by acetate in the growth medium. A comparative Northern (RNA) analysis of the C. glutamicum isocitrate lyase and malate synthase genes (aceA and aceB) and transcriptional cat fusion experiments revealed that aceA and aceB are transcribed as 1.6-and 2.7-kb monocistronic messages, respectively, and that the regulation of isocitrate lyase and malate synthase synthesis is exerted at the level of transcription from the respective promoters. Surprisingly, C. glutamicum mutants defective in either acetate kinase or phosphotransacetylase showed low specific activities of the other three enzymes (phosphotransacetylase, isocitrate lyase, and malate synthase or acetate kinase, isocitrate lyase, and malate synthase, respectively) irrespective of the presence or absence of acetate in the medium. This result and a correlation of a high intracellular acetyl coenzyme A concentration with high specific activities of isocitrate lyase, malate synthase, acetate kinase, and phosphotransacetylase suggest that acetyl coenzyme A or a derivative thereof may be a physiological trigger for the genetic regulation of enzymes involved in acetate metabolism of C. glutamicum.