Kretzschmar Utta, Rückert Andreas, Jeoung Jae-Hun, Görisch Helmut
Fachgebiet Technische Biochemie, Institut für Biotechnologie der Technischen Universität Berlin, Seestraße 13, D-13353 Berlin, Germany1.
Microbiology (Reading). 2002 Dec;148(Pt 12):3839-3847. doi: 10.1099/00221287-148-12-3839.
Pseudomonas aeruginosa ATCC 17933 growing aerobically on ethanol uses a pyrroloquinoline quinone-dependent ethanol oxidation system. A mutant with an interrupted putative mqo gene, in which malate:quinone oxidoreductase (MQO), an enzyme involved in the citric acid cycle/glyoxylate cycle, was defective, showed a severe growth defect on ethanol and was unable to grow on acetate. Glucose, lactate, succinate or malate supported growth of the mutant. However, an NAD-dependent malate dehydrogenase activity could not be detected. Complementation of the mutant by the wild-type allele of the mqo gene restored wild-type behaviour. The wild-type expressed the dye-dependent MQO and NAD(P)-dependent malic enzymes (MEs). Pyruvate carboxylase (PC) was found upon growth of the wild-type and the mutant on all substrates studied. PC activity in the wild-type was induced on glucose and lactate and was always higher on all substrates in the mqo mutant. In P. aeruginosa ATCC 17933, an active MQO is required for growth on ethanol or acetate, while with glucose, lactate, succinate or malate an apparent bypass route operates, with MEs using malate for generating pyruvate, which is carboxylated to oxaloacetate by PC. To the authors' knowledge, this is the first time that a specific mutant MQO phenotype has been observed, caused by the inactivation of a gene encoding MQO activity. mqo of P. aeruginosa ATCC 17933 corresponds to mqoB (PA4640) of the P. aeruginosa PAO1 genome project.
铜绿假单胞菌ATCC 17933在乙醇上进行有氧生长时，使用一种依赖吡咯喹啉醌的乙醇氧化系统。一个假定的mqo基因被中断的突变体，其中参与柠檬酸循环/乙醛酸循环的苹果酸：醌氧化还原酶（MQO）有缺陷，该突变体在乙醇上表现出严重的生长缺陷，并且无法在乙酸盐上生长。葡萄糖、乳酸、琥珀酸或苹果酸能支持该突变体生长。然而，未检测到NAD依赖的苹果酸脱氢酶活性。用mqo基因的野生型等位基因对该突变体进行互补，恢复了野生型的表型。野生型表达了染料依赖的MQO和NAD（P）依赖的苹果酸酶（MEs）。在野生型和突变体在所有研究的底物上生长时都发现了丙酮酸羧化酶（PC）。野生型中的PC活性在葡萄糖和乳酸上被诱导，并且在mqo突变体中所有底物上的活性总是更高。在铜绿假单胞菌ATCC 17933中，在乙醇或乙酸盐上生长需要有活性的MQO，而对于葡萄糖、乳酸、琥珀酸或苹果酸，一条明显的旁路途径起作用，MEs利用苹果酸生成丙酮酸，丙酮酸再被PC羧化生成草酰乙酸。据作者所知，这是首次观察到由编码MQO活性的基因失活导致的特定突变体MQO表型。铜绿假单胞菌ATCC 17933的mqo对应于铜绿假单胞菌PAO1基因组计划中的mqoB（PA4640）。
