Creaghan I T, Guest J R
J Gen Microbiol. 1978 Jul;107(1):1-13. doi: 10.1099/00221287-107-1-1.
Lipoic acid (lip) and 2-oxoglutarate dehydrogenase (sucA) mutants of Escherichia coli K12 exhibit a requirement for exogenous succinate during aerobic growth on glucose minimal medium. Reversion studies have shown that this requirement can be suppressed by gal-linked mutations which inactivate succinate dehydrogenase. Biochemical and genetic studies confirmed that the succinate dehydrogenase gene (sdh) is affected and that suppression is mediated by the same intergenic and indirect mechanism that generates succinate independence in partial revertants of lipoamide dehydrogenase mutants (Creaghan & Guest, 1977). A series of isogenic strains containing all combinations of mutations affecting 2-oxoglutarate dehydrogenase (sucA), succinate dehydrogenase (sdh), isocitrate lyase (aceA) and fumarate reductase (frd) in a background lacking succinate semialdehyde dehydrogenase, was constructed to assess the importance of these enzymes as sources of endogenous succinate (succinyl-CoA) during aerobic and anaerobic growth on glucose. Only strains combining a deficiency in 2-oxoglutarate dehydrogenase with the presence of an active succinate dehydrogenase required succinate for aerobic growth. In all mutants, including the triple mutant (frd sucA aceA), the succinate requirement was suppressed by inactivating succinate dehydrogenase. The aerobic growth rates of succinate-independent strains were most affected by lack of isocitrate lyase but only two mutants (sdh sucA aceA and frd sdh sucA aceA) grew faster with added succinate: the growth yields were lowered by deficiencies in isocitrate lyase and also succinate dehydrogenase. It is concluded that very little succinate is needed for biosynthesis during aerobic growth on glucose and the requirement for relatively high concentrations of succinate (2 mM) by mutants lacking 2-oxoglutarate dehydrogenase or related functions stems from the presence of active succinate dehydrogenase. Anaerobically, either isocitrate lyase or fumarate reductase is essential for succinate-independent growth on glucose.
大肠杆菌K12的硫辛酸（lip）和2-氧代戊二酸脱氢酶（sucA）突变体在以葡萄糖为唯一碳源的基本培养基上有氧生长时，对外源琥珀酸有需求。回复突变研究表明，这种需求可被使琥珀酸脱氢酶失活的gal连锁突变所抑制。生化和遗传学研究证实，琥珀酸脱氢酶基因（sdh）受到影响，并且抑制作用是由与硫辛酰胺脱氢酶突变体部分回复株中产生琥珀酸非依赖性相同的基因间间接机制介导的（Creaghan和Guest，1977）。构建了一系列同基因菌株，它们在缺乏琥珀酸半醛脱氢酶的背景下，包含影响2-氧代戊二酸脱氢酶（sucA）、琥珀酸脱氢酶（sdh）、异柠檬酸裂合酶（aceA）和延胡索酸还原酶（frd）的所有突变组合，以评估这些酶在以葡萄糖为底物的有氧和无氧生长过程中作为内源性琥珀酸（琥珀酰辅酶A）来源的重要性。只有那些2-氧代戊二酸脱氢酶缺陷且同时存在活性琥珀酸脱氢酶的菌株在有氧生长时需要琥珀酸。在所有突变体中，包括三突变体（frd sucA aceA），通过使琥珀酸脱氢酶失活可抑制对琥珀酸的需求。缺乏异柠檬酸裂合酶对琥珀酸非依赖性菌株的有氧生长速率影响最大，但只有两个突变体（sdh sucA aceA和frd sdh sucA aceA）在添加琥珀酸时生长得更快：异柠檬酸裂合酶和琥珀酸脱氢酶的缺陷都会降低生长产量。结论是，在以葡萄糖为底物的有氧生长过程中，生物合成所需的琥珀酸极少，缺乏2-氧代戊二酸脱氢酶或相关功能的突变体对相对高浓度琥珀酸（2 mM）的需求源于活性琥珀酸脱氢酶的存在。在无氧条件下，异柠檬酸裂合酶或延胡索酸还原酶对于以葡萄糖为底物的琥珀酸非依赖性生长至关重要。
