Alvarez M A, Fu H, Khosla C, Hopwood D A, Bailey J E
Institute of Biotechnology, ETH, Zürich, Switzerland.
Nat Biotechnol. 1996 Mar;14(3):335-8. doi: 10.1038/nbt0396-335.
The ORFVI from the cluster of genes, which is responsible for the biosynthesis of the Streptomyces coelicolor spore pigment, the whiE cluster, has been described as a bifunctional aromatase/cyclase. In order to evaluate its potential use for generating novel polyketides, combinations of this gene with those encoding minimal polyketide synthase enzymes with or without a ketoreductase from S. coelicolor A3(2) were constructed and analyzed in vivo. Analysis of the polyketide products generated from these constructs indicates that the whiE-ORFVI enzyme has properties similar to those of TcmN, although the whiE aromatase/cyclase normally acts on a polyketide intermediate that is four carbons longer than the TcmN substrate. The whiE aromatase/cyclase can influence the regiospecificity of the first cyclization of unreduced, but not reduced, backbones and is also responsible for the second ring aromatization. An unusual new polyketide, EM18, was identified which is not seen in equivalent strains expressing the tcmN aromatase/cyclase or the act aromatase genes. The structure of EM18 suggests that the WhiE-ORFVI product might have some unique properties within this family of polyketide synthase subunits, and may therefore be useful in the design of combinatorial biosynthetic strategies.
来自基因簇的ORFVI负责天蓝色链霉菌孢子色素（whiE基因簇）的生物合成，已被描述为一种双功能芳香化酶/环化酶。为了评估其在生成新型聚酮化合物方面的潜在用途，构建了该基因与编码最小聚酮合酶的基因的组合，这些最小聚酮合酶带有或不带有来自天蓝色链霉菌A3(2)的酮还原酶，并在体内进行了分析。对这些构建体产生的聚酮化合物产物的分析表明，whiE-ORFVI酶具有与TcmN相似的特性，尽管whiE芳香化酶/环化酶通常作用于比TcmN底物长四个碳的聚酮中间体。whiE芳香化酶/环化酶可以影响未还原而非还原主链第一次环化的区域特异性，并且还负责第二个环的芳香化。鉴定出一种不寻常的新聚酮化合物EM18，在表达tcmN芳香化酶/环化酶或act芳香化酶基因的等效菌株中未见到。EM18的结构表明，WhiE-ORFVI产物在该聚酮合酶亚基家族中可能具有一些独特的特性，因此可能有助于组合生物合成策略的设计。
