REGULATION OF CLOSTRIDIUM-ACETOBUTYLICUM METABOLISM AS REVEALED BY MIXED-SUBSTRATE STEADY-STATE CONTINUOUS CULTURES - ROLE OF NADH/NAD RATIO AND ATP POOL
REGULATION OF CLOSTRIDIUM-ACETOBUTYLICUM METABOLISM AS REVEALED BY MIXED-SUBSTRATE STEADY-STATE CONTINUOUS CULTURES - ROLE OF NADH/NAD RATIO AND ATP POOL
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DOI：
10.1128/jb.176.21.6433-6438.1994
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发表时间：
1994-11-01
影响因子：
3.2
通讯作者：
SOUCAILLE, P
中科院分区：
文献类型：
--
作者：
GIRBAL, L;SOUCAILLE, P
甘油-葡萄糖补料（摩尔比为 2）的丙酮丁醇梭菌恒化培养物葡萄糖有限，但甘油充足，并且具有高细胞内 NADH/NAD 比率（I. Vasconcelos，L. Girbal，和 P. Soucaille，J. Bacteriol，176：1443-1450，1994）。我们在此报告，3-磷酸甘油醛脱氢酶是糖酵解途径的关键酶之一，会受到高 NADH/NAD 比率的抑制。用丙酮酸部分替代葡萄糖，同时将甘油浓度维持在恒定水平，使得稳态连续培养物中甘油的消耗量更高。然而，甘油充足的培养物具有通过 3-磷酸甘油醛脱氢酶的恒定通量和恒定的 NADH/NAD 比率。用丙酮酸高度取代葡萄糖[P/(G+P)值为0.67 g/g]提供了以丁醇和丁酸作为主要最终产物的碳限制培养物。在这种产酒精培养物中，NADH依赖性丁醛和铁氧还蛋白-NAD(P)还原酶的诱导以及乙醇脱氢酶的较高表达与高NADH/NAD比率和低细胞内ATP浓度有关。在三种不同的稳态培养物中，体外磷酸转丁酰酶和丁酸激酶活性随着细胞内 ATP 浓度的增加而降低，表明这些排列在操纵子中的 Cove 基因存在转录调节
Glycerol-glucose-fed (molar ratio of 2) chemostat cultures of Clostridium acetobutylicum were glucose limited but glycerol sufficient and had a high intracellular NADH/NAD ratio (I. Vasconcelos, L. Girbal, and P. Soucaille, J. Bacteriol, 176:1443-1450, 1994). We report here that the glyceraldehyde-3-phosphate dehydrogenase, one of the key enzymes of the glycolytic pathway, is inhibited by high NADH/NAD ratios. Partial substitution of glucose by pyruvate while maintaining glycerol concentration at a constant level allowed a higher consumption of glycerol in steady-state continuous cultures. However, glycerol-sufficient cultures had a constant flux through the glyceraldehyde-3-phosphate dehydrogenase and a constant NADH/NAD ratio. A high substitution of glucose by pyruvate [P/(G+P) value of 0.67 g/g] provided a carbon-limited culture with butanol and butyrate as the major end products. In this alcohologenic culture, the induction of the NADH-dependent butyraldehyde and the ferredoxin-NAD(P) reductases and the higher expression of alcohol dehydrogenases were related to a high NADH/NAD ratio and a low intracellular ATP concentration. In three different steady-state cultures, the in vitro phosphotransbutyrylase and butyrate-kinase activities decreased with the intracellular ATP concentration, suggesting a transcriptional regulation of these Cove genes, which are arranged in an operon