engleski

In silico generation of novel polyketides for the use in agro-industry

Many polyketide compounds are used in the agro-industry including antiparasitics (e.g. avermectin), coccidiostatics (e.g. monensin), animal growth promoters (e.g. virginiamycin) and insecticides (e.g. spynosin). Traditional screening programmes suffer from the disadvantage that subsequent purification and characterisation of compounds is slow and labour intensive. Combinatorial chemistry looked promising, but failed to produce bioactive compounds. The modular polyketide biosynthesis clusters (PKS) in Streptomyces synthesise polyketides in a step-wise manner and the extender unit incorporated at each step is specified by its own module in the large PKS enzyme. Combinatorial biosynthesis, which combines modules of different specificity using recombinant DNA technology should produce a large number of polyketide products. Although such approaches can produce the predicted products, the yield is usually extremely low restricting their practical application. It seemed likely that the low yield resulted from unsuitable junctions between modules. Homologous recombination, which should be important in the natural evolution of new PKS clusters, favours closely related sequences and should result in better junctions and higher yields. It was, therefore, decided to model homologous recombination between known PKS clusters in silico. The program CompGen predicted the number of recombinants that would be produced and using a specially constructed database to link genetic structure to biosynthesis, it was possible to predict the novel chemical structures of the linear polyketide backbone produced by recombinants. The problems of predicting the cyclisation of these structures will be discussed. A second program ClustScan was developed to annotate new clusters and, thus, expand the number of substrates for CompGen.

polyketides; streptomyces; homologous recombination

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