Negoro S, Kato K, Fujiyama K, Okada H
Department of Biotechnology, Osaka University, Japan.
Biodegradation. 1994 Dec;5(3-4):185-94. doi: 10.1007/BF00696459.
This review article is a compendium of the available information on the degradation of a man-made compound, 6-aminohexanoate-oligomer, in Flavobacterium and Pseudomonas strains, and discusses the molecular basis for adaptation of microorganisms toward these xenobiotic compounds. Three plasmid-encoded enzymes, 6-aminohexanoate-cyclic-dimer hydrolase (EI), 6-aminohexanoate-dimer hydrolase (EII), and endo-type 6-aminohexanoate-oligomer hydrolase (EIII) are responsible for the degradation of the oligomers. Two repeated sequences, designated RS-I and RS-II, are found on plasmid pOAD2, which is involved in 6-aminohexanoate degradation in Flavobacterium. RS-I appears 5 times on the pOAD2, and all copies have the same sequences as insertion sequence IS6100. RS-II appears twice on the plasmid. RS-IIA contains the gene encoding EII, while RS-IIB contains the gene for the analogous EII' protein. Both EII and EII' are polypeptides of 392 amino acids, which differ by 46 amino acid residues. The specific activity of the EII enzyme is 200-fold higher than that of EII'. Construction of various hybrid genes demonstrated that only the combination of two amino acid residues in the EII' enzyme can enhance the activity of the EII' to the same level as that of EII enzyme.
这篇综述文章汇编了关于黄杆菌属和假单胞菌属菌株中人造化合物6-氨基己酸酯低聚物降解的现有信息，并讨论了微生物对这些异源生物化合物适应性的分子基础。三种质粒编码的酶，6-氨基己酸环二聚体水解酶（EI）、6-氨基己酸二聚体水解酶（EII）和内切型6-氨基己酸酯低聚物水解酶（EIII）负责低聚物的降解。在参与黄杆菌属中6-氨基己酸降解的质粒pOAD2上发现了两个重复序列，命名为RS-I和RS-II。RS-I在pOAD2上出现5次，所有拷贝都具有与插入序列IS6100相同的序列。RS-II在质粒上出现两次。RS-IIA包含编码EII的基因，而RS-IIB包含类似EII'蛋白的基因。EII和EII'都是由392个氨基酸组成的多肽，它们相差46个氨基酸残基。EII酶的比活性比EII'高200倍。各种杂交基因的构建表明，只有EII'酶中的两个氨基酸残基组合才能将EII'的活性提高到与EII酶相同的水平。
