Gene Cloning,Heterologous Expression And Substrate Specificity Of Sargassum Fusiforme Polyketide Synthase

The brown algae polyphenols are natural bioactive products with high content in Sargassum fusiforme.From the perspective of structure,they are only formed from the polymerization of phloroglucinol monomers despite the diversity of structures.Styduties on Ectocarpus siliculosus indicate that polyketide synthase gene(PKS)is a key gene in the biosynthetic pathway of the monomer.Homology analysis indicates that there is a polyketide synthase gene in Sargassum fusiforme,which has very high homology with the former;in addition,there are two other polyketide synthase genes in Sargassum fusiforme,but their functions are still unknown.In this paper,the gene cloning,heterologous expression and the enzymological analysis of the polysynthase synthase are studied.There are three polyketide synthase genes,namely SfPKS1,SfPKS2 and SfPKS3.which are cloned.The genes were heterologously expressed in E.coli,and the purified recombinant proteins were studied for their enzymatic properties.Homology analysis of SfPKS genes showes that SfPKS2 and SfPKS3 have high similarity,and have higher homology with SbPKS and EsiPKS1;meanwhile,the SfPKS amino acid sequence of the substrate recognition sites and catalytically active sites are highly conserved.Two types of CoA-linear alkyl CoA and aromatic CoA were tested by the catalytic substrate of SfPKS.The result showed that SfPKS can synthesize the corresponding products with aromatic CoA as the reaction substrate.The study on SfPKS can help to mine other polyketides in Sargassum fusiformis and lay a foundation for further research and utilization of related natural products.