Okada H, Negoro S, Kimura H, Nakamura S
Nature. 1983;306(5939):203-6. doi: 10.1038/306203a0.
Flavobacterium sp. KI72 metabolizes 6-aminohexanoic acid cyclic dimer, a by-product of nylon manufacture, through two newly evolved enzymes, 6-aminohexanoic acid cyclic dimer hydrolase (EI) and 6-aminohexanoic acid linear oligomer hydrolase (EII). These enzymes are active towards man-made compounds, the cyclic dimer and linear oligomers of 6-aminohexanoic acid respectively, but not towards any of the natural amide bonds tested. The structural genes of EI (nylA) and EII (nylB) are encoded on pOAD2, one of three plasmids harboured in Flavobacterium sp. KI72. This plasmid contains two kinds of repeated sequence (RS-I and RS-II); one of the two RS-II sequences, RS-IIA, contains the nylB gene, while the other, RS-IIB, contains a homologous nylB' gene. From comparisons of the nucleotide sequences and gene products of the nylB and nylB' genes, we now conclude that EII enzyme is newly evolved by gene duplication followed by base substitutions on the same plasmid.
黄杆菌属菌株KI72通过两种新进化出的酶，即6-氨基己酸环状二聚体水解酶（EI）和6-氨基己酸线性寡聚体水解酶（EII），代谢尼龙制造的副产物6-氨基己酸环状二聚体。这些酶分别对人造化合物6-氨基己酸的环状二聚体和线性寡聚体有活性，但对所测试的任何天然酰胺键均无活性。EI（nylA）和EII（nylB）的结构基因编码在pOAD2上，pOAD2是黄杆菌属菌株KI72所携带的三种质粒之一。该质粒包含两种重复序列（RS-I和RS-II）；两个RS-II序列之一，即RS-IIA，包含nylB基因，而另一个RS-IIB包含同源的nylB'基因。通过对nylB和nylB'基因的核苷酸序列和基因产物的比较，我们现在得出结论，EII酶是通过基因复制，然后在同一质粒上发生碱基替换而新进化出来的。
