ENERGETIC ASPECTS OF GLUCOSE-METABOLISM IN A PYRUVATE-DEHYDROGENASE-NEGATIVE MUTANT OF SACCHAROMYCES-CEREVISIAE
ENERGETIC ASPECTS OF GLUCOSE-METABOLISM IN A PYRUVATE-DEHYDROGENASE-NEGATIVE MUTANT OF SACCHAROMYCES-CEREVISIAE
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DOI：
10.1099/00221287-140-3-601
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发表时间：
1994-03-01
期刊：
影响因子：
2.8
通讯作者：
VANDIJKEN, JP
中科院分区：
文献类型：
--
作者：
PRONK, JT;WENZEL, TJ;VANDIJKEN, JP
酿酒酵母T23 C（pda 1：：Tn 5 ble）是野生型酿酒酵母S.酿酒酵母T23 D。突变导致丙酮酸脱氢酶活性完全丧失。丙酮酸脱氢酶阴性（Pdh（-））菌株的丙酮酸代谢在有氧葡萄糖限制恒化培养中进行了研究，以0.10 h（-1）的稀释率生长，并与同基因野生型菌株的代谢进行了比较。在这些条件下，Pdh（-）菌株的生长是完全呼吸的。无细胞提取物中的酶活性表明，丙酮酸脱羧酶、乙醛脱氢酶和乙酰辅酶A（乙酰辅酶A）合成酶可以提供丙酮酸脱氢酶复合物的功能旁路。由于该代谢序列涉及乙酰辅酶A合成酶反应中的ATP水解，因此预期pda 1：：Tn 5 ble突变对生长效率的负面影响。实际上，Pdh（-）菌株的生物量产率[0.44 g生物量（g葡萄糖）（-1）]显著低于野生型S.酿酒酵母[0.52 g生物质（g葡萄糖）（-1）]。突变对生物量产量的影响可以定量地解释为葡萄糖催化剂的ATP产量较低，而乙酰辅酶A合成所需的ATP增加。对照实验表明，pda 1：：Tn 5 ble突变不影响乙醇限制恒化培养物的生物量产量。结果支持了这样的观点：在有氧葡萄糖限制生长期间，S。在低生长速率的酿酒酵母中，丙酮酸脱氢酶复合物占丙酮酸通量的主要部分。此外，可以得出结论，在乙酰辅酶A合成酶反应中形成的焦磷酸的水解并不显着有助于在这种酵母中的能量转导。在恒化器培养物中，呼吸缺陷细胞对葡萄糖代谢没有贡献，并且可能在平板接种时形成。
Saccharomyces cerevisiae T23C (pda1::Tn5ble) is an isogenic gene replacement mutant of the wild-type strain S. cerevisiae T23D. The mutation causes a complete loss of pyruvate dehydrogenase activity. Pyruvate metabolism in this pyruvate-dehydrogenase- negative (Pdh(-)) strain was investigated in aerobic glucose-limited chemostat cultures, grown at a dilution rate of 0.10 h(-1), and compared with the metabolism in the isogenic wild-type strain. Under these conditions, growth of the Pdh(-) strain was fully respiratory. Enzyme activities in cell-free extracts indicated that the enzymes pyruvate decarboxylase, acetaldehyde dehydrogenase and acetyl-coenzyme A (acetyl-CoA) synthetase could provide a functional bypass of the pyruvate dehydrogenase complex. Since this metabolic sequence involves ATP hydrolysis in the acetyl-CoA synthetase reaction, a negative effect of the pda1::Tn5ble mutation on the growth efficiency was anticipated. Indeed, the biomass yield of the Pdh(-) strain [0.44 g biomass (g glucose)(-1)] was significantly lower than that of wild-type S. cerevisiae [0.52 g biomass (g glucose)(-1)]. The effect of the mutation on biomass yield could be quantitatively explained in terms of a lower ATP yield from glucose catabolism and an increased ATP requirement for the synthesis of acetyl-CoA used in anabolism. Control experiments showed that the pda1::Tn5ble mutation did not affect biomass yield in ethanol-limited chemostat cultures. The results support the view that, during aerobic glucose-limited growth of S. cerevisiae at low growth rates, the pyruvate dehydrogenase complex accounts for the major part of the pyruvate flux. Moreover, it is concluded that hydrolysis of pyrophosphate formed in the acetyl-CoA synthetase reaction does not contribute significantly to energy transduction in this yeast. Respiratory-deficient cells did not contribute to glucose metabolism in the chemostat cultures and were probably formed upon plating.