Görisch Helmut
Fachgebiet Technische Biochemie, Institut für Biotechnologie der Technischen Universität Berlin, Seestrasse 13, D-13353 Berlin, Germany.
Biochim Biophys Acta. 2003 Apr 11;1647(1-2):98-102. doi: 10.1016/s1570-9639(03)00066-9.
Pseudomonas aeruginosa ATCC 17933, when growing on ethanol, uses a pyrroloquinoline quinone (PQQ)-dependent ethanol oxidation system. The genes coding for the ethanol oxidizing enzyme, a quinoprotein ethanol dehydrogenase (QEDH), cytochrome c(550), which is an essential component of the electron transport chain and accepts the electrons from QEDH, and an NAD-dependent acetaldehyde dehydrogenase form the exaABC gene cluster. Downstream of the exaBC genes the pqqABCDE gene cluster is found, which codes for proteins essential for biosynthesis of the cofactor PQQ. Also essential for growth on ethanol are an acetyl-CoA synthetase encoded by the acsA gene and a malate:quinone oxidoreductase encoded by the mqo gene. The X-ray structure of the soluble QEDH from P. aeruginosa was solved. It is a homodimeric enzyme and, aside from differences in some loops, the folding of QEDH is very similar to the large subunit of the soluble methanol dehydrogenase of methylotrophs, and the PQQ domain of the quinohemoprotein alcohol dehydrogenase from Comamonas testosteroni and P. fluorescens. Transcription from the QEDH (exaA) promoter is regulated by a two component system: a histidine sensor kinase (ExaD), which is presumably located in the cytoplasm, and a response regulator (ExaE). The phenotypic characterization and transcription studies with six regulatory mutants indicate that seven different genes in an hierarchical organization may be involved in regulating the transcription of the ethanol oxidation system and components of acetate metabolism in P. aeruginosa.
铜绿假单胞菌ATCC 17933在以乙醇为碳源生长时，利用一种依赖于吡咯喹啉醌（PQQ）的乙醇氧化系统。编码乙醇氧化酶（一种醌蛋白乙醇脱氢酶（QEDH））、细胞色素c（550）（电子传递链的必需组分，接受来自QEDH的电子）以及一种NAD依赖的乙醛脱氢酶的基因形成了exaABC基因簇。在exaBC基因的下游发现了pqqABCDE基因簇，其编码辅因子PQQ生物合成所必需的蛋白质。acsA基因编码的乙酰辅酶A合成酶和mqo基因编码的苹果酸：醌氧化还原酶对于在乙醇上生长也至关重要。已解析了来自铜绿假单胞菌的可溶性QEDH的X射线结构。它是一种同二聚体酶，除了一些环的差异外，QEDH的折叠与甲基营养菌可溶性甲醇脱氢酶的大亚基、睾丸酮丛毛单胞菌和荧光假单胞菌的醌血红蛋白醇脱氢酶的PQQ结构域非常相似。QEDH（exaA）启动子的转录由一个双组分系统调控：一个可能位于细胞质中的组氨酸传感器激酶（ExaD）和一个响应调节因子（ExaE）。对六个调控突变体的表型特征分析和转录研究表明，在铜绿假单胞菌中，一个层次组织中的七个不同基因可能参与调控乙醇氧化系统和乙酸代谢组分的转录。
