Advances on polyketide biosynthesise by microorganism and the diversity of polyketide synthases 多聚酮的微生物合成及其多样性研究进展
2.
The results showed that the f fragment , 728bp in length , could be a new gene with a little homology to the genes coding for polyketide synthetase or fatty - acid synthetase and the b fragment , about 4kb in length , is inferred to have repeat sequences around tn5 insertion site , in which there is homology to the wa 314 right arm of the high - pathogeniciry island of yersinia enterocolitica . to reveal any pathogenicity of enterobacter cloacae b8 and its mutated strains b8b and b8f to animals , the experiment with mice was carried out 结果显示， f片段长度为728bp ，与现有生物数据库的blast比较分析，发现该序列仅有局部短于1oobp的区域与polyketide合成酶基因或与脂肪酸合成酶基因有低的同源性，推测为一新基因； b片段长约4kb ，序列拼接结果推测靠近tn5插入位点部位有重复序列，对b片段tn5远端的部分序列进行blast比较，发现它与小肠结肠炎耶尔森氏菌的强毒力岛有一定的同源性。
3.
In addition to avermectins , s . avermitilis produces oligomycin , a strongly toxic compound . gene deletion vector pxl05 was used to disrupt oligomycin polyketide synthase ( pks ) encoding genes ( olma ) in streptomyces avermitilis cz8 - 73 , the producer of anthelmintic avermectins b and the cell growth inhibitor oligomycin . olma gene cluster in the chromosome was displaced by deletion allele on the plasmid via double crossover 本研究以产阿维菌素b和寡霉素的阿维链霉菌cz8 - 73为出发菌株，构建了基因缺失载体pxl05 ，并将其转入cz8 - 73中，通过缺失载体和染色体之间的同源双交换，对染色体上长达90kb的寡霉素聚酮合酶( pks )基因簇( olma )进行了缺失。
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In consideration of the colinearity between the activities of avermectin pks domains and structure of the polyketide product , the dh2 domain of avermectin pks , which corresponds to c - 22 , 23 dehydration , appears to have partial dehydratase activity and this results in a mixture of c - 22 , 23 double bonds ( " 1 " components ) and c23 hydroxy compounds ( " 2 " components ) 目前国内外尚未见有关仅产阿维菌素b1菌株的报道。根据阿维菌素pks基因结构与其聚酮合成反应步骤之间的线性关系，推测b2组分的产生可能是由于阿维菌素pks模块2中脱水酶( dh )的不完全活性所造成。
