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首页> 外文期刊>Journal of bacteriology >Regulation of Carbon and Electron Flow inClostridium butyricum VPI 3266 Grown on Glucose-Glycerol Mixtures
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Regulation of Carbon and Electron Flow inClostridium butyricum VPI 3266 Grown on Glucose-Glycerol Mixtures

机译：葡萄糖-甘油混合物中生长的丁酸梭菌VPI 3266中碳和电子流量的调节

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The metabolism of Clostridium butyricum was manipulated at pH 6.5 and in phosphate-limited chemostat culture by changing the overall degree of reduction of the substrate using mixtures of glucose and glycerol. Cultures grown on glucose alone produced only acids (acetate, butyrate, and lactate) and a high level of hydrogen. In contrast, when glycerol was metabolized, 1,3-propanediol became the major product, the specific rate of acid formation decreased, and a low level of hydrogen was observed. Glycerol consumption was associated with the induction of (i) a glycerol dehydrogenase and a dihydroxyacetone kinase feeding glycerol into the central metabolism and (ii) an oxygen-sensitive glycerol dehydratase and an NAD-dependent 1,3-propanediol dehydrogenase involved in propanediol formation. The redirection of the electron flow from hydrogen to NADH formation was associated with a sharp decrease in the in vitro hydrogenase activity and the acetyl coenzyme A (CoA)/free CoA ratio that allows the NADH-ferredoxin oxidoreductase bidirectional enzyme to operate so as to reduce NAD in this culture. The decrease in acetate and butyrate formation was not explained by changes in the concentration of phosphotransacylases and acetate and butyrate kinases but by changes in in vivo substrate concentrations, as reflected by the sharp decrease in the acetyl-CoA/free CoA and butyryl-CoA/free CoA ratios and the sharp increase in the ATP/ADP ratio in the culture grown with glucose and glycerol compared with that in the culture grown with glucose alone. As previously reported for Clostridium acetobutylicum (L. Girbal, I. Vasconcelos, and P. Soucaille, J. Bacteriol. 176:6146–6147, 1994), the transmembrane pH of C. butyricum is inverted (more acidic inside) when the in vivo activity of hydrogenase is decreased (cultures grown on glucose-glycerol mixture). For both cultures, the stoichiometry of the H+ ATPase was shown to remain constant and equal to 3 protons exported per molecule of ATP consumed.
机译：通过改变葡萄糖和甘油混合物对底物的总体还原程度，可在pH 6.5和磷酸盐限制的恒化器培养物中控制丁酸梭菌的代谢。仅靠葡萄糖生长的培养物仅产生酸（乙酸盐，丁酸盐和乳酸盐）和高水平的氢。相反，当甘油被代谢时，1,3-丙二醇成为主要产物，酸形成的比速率降低，并且观察到低水平的氢。甘油的消耗与诱导（i）将甘油供入中枢代谢的甘油脱氢酶和二羟基丙酮激酶以及（ii）参与丙二醇形成的氧敏感性甘油脱水酶和NAD依赖的1,3-丙二醇脱氢酶相关。电子流从氢向NADH形成的重定向与体外氢化酶活性的急剧下降以及乙酰辅酶A（CoA）/游离CoA的比率降低有关，该比率允许NADH-铁氧还蛋白氧化还原酶双向酶起作用从而降低NAD在这种文化中。乙酸盐和丁酸盐形成的减少不是通过磷酸转酰酶和乙酸盐和丁酸盐激酶的浓度变化来解释，而是通过体内底物浓度的变化来解释，这反映在乙酰基-CoA /游离CoA和丁酰-CoA /的急剧下降中。与仅用葡萄糖生长的培养物相比，用葡萄糖和甘油生长的培养物的游离CoA比率和ATP / ADP比率的急剧增加。如先前报道的丙酮丁醇梭菌（L. Girbal，I. Vasconcelos和P. Soucaille，J. Bacteriol。176：6146-6147，1994）， C的跨膜pH值。当氢化酶的体内活性降低时（在葡萄糖-甘油混合物上生长的培养物），丁酸倒转（内部更酸性）。对于两种培养物，H + ATPase的化学计量均显示为恒定，等于每消耗一分子的ATP输出3个质子。

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