Jones P W, Turner J M
J Gen Microbiol. 1984 Apr;130(4):849-60. doi: 10.1099/00221287-130-4-849.
By varying the composition of the growth medium and the genotype of the bacterial strain, five isoenzymes of CoA-dependent aldehyde dehydrogenase could be detected in Escherichia coli. Two isoenzymes (A, mol. wt 520 000; and B, mol. wt 370 000) were produced only in the presence of ethanolamine and vitamin (or coenzyme) B12 ('inducible isoenzymes'), whereas the other three isoenzymes (C, mol. wt 900 0000; D, mol. wt 120 000; and E, mol. wt 720 000) were produced only in the absence of ethanolamine and vitamin B12 ('repressible isoenzymes'). Partial purification and characterization of these isoenzymes revealed strong similarities, with respect to pH optima and substrate affinities, between isoenzymes within either of the two classes, but significant differences between the two classes. Mutant studies demonstrated that the relationships between the isoenzymes and between CoA-dependent aldehyde dehydrogenase and ethanolamine ammonia-lyase are both structural and regulatory in nature, and a two-operon model is proposed to account for the common control of the enzymes of ethanolamine catabolism in E. coli.
通过改变生长培养基的成分和细菌菌株的基因型，在大肠杆菌中可检测到五种辅酶A依赖性醛脱氢酶的同工酶。两种同工酶（A，分子量520 000；和B，分子量370 000）仅在存在乙醇胺和维生素（或辅酶）B12的情况下产生（“诱导型同工酶”），而其他三种同工酶（C，分子量900 0000；D，分子量120 000；和E，分子量720 000）仅在不存在乙醇胺和维生素B12的情况下产生（“可阻遏同工酶”）。对这些同工酶的部分纯化和特性分析表明，在两类同工酶各自内部，就最适pH值和底物亲和力而言，它们有很强的相似性，但两类之间存在显著差异。突变体研究表明，同工酶之间以及辅酶A依赖性醛脱氢酶和乙醇胺氨裂解酶之间的关系在本质上既是结构上的也是调节上的，并且提出了一个双操纵子模型来解释大肠杆菌中乙醇胺分解代谢酶的共同调控。
