Intermediates and enzymes involved in fluorometabolite biosynthesis in Streptomyces cattleya

Metabolites;Enzymes;Streptomyces

McGlinchey, Ryan ; O'Hagan, David ; O'Hagan, David

University:University of St Andrews

Department:Chemistry (School of)

关键词: Metabolites;    Enzymes;    Streptomyces;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/11000/RyanMcGlincheyPhDThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

Enzymatic halogenation occurs during the biosynthesis of more than 4,000 naturalproducts. The presence of fluorinated natural products is much less common, with only 13reported to date. The bacterium Streptomyces cattleya is known to biosynthesise twofluorinated secondary metabolites, fluoroacetate and 4-fluorothreonine. The precursor tothese secondary metabolites is known to be fluoroacetaldehyde. It had previously beenshown that a fluorination enzyme mediates a reaction between S-adenosyl-L-methionine(SAM) and F to generate 5'-fluoro-5'-deoxyadenosine (5'-FDA). This is the firstcommitted step on the biosynthetic pathway. The pathway between 5' -FDA andfluoroacetaldehyde had not been investigated in detail prior to the work carried out in thisthesis.A purine nucleoside phosphorylase has been partially purified from cell-free extractswhich catalyses the phosphorolytic cleavage of 5'-FDA to 5-fluoro-5-deoxY-D-ribose-1-phosphate (5-FDRP). Substrate specificity shows a profile which shares a close similarityto bacterial 5'-methylthioadenosine phosphorylases (MTAP's). The identification of a genecluster encoding enzymes responsible for fluorometabolite biosynthesis shows the PNPgene located adjacent to the fluorinase gene, reinforcing the involvement of this enzyme inthe fluorometabolite pathway.It is shown that 5-FDRP is converted to 5-fluoro-5-deoxy-D-ribulose-1-phosphate (5-FDRibP) via an isomerase activity. The enzyme responsible for this transformation hasbeen partially purified from cell free extracts (CFE's). Another metabolite was identifiedas 5-fluoro-5-deoxY-D-xylulose-l-phosphate (5-FDXyuP), a diastereoisomer of 5-FDRibP,which appears to be an adventitious product in CFE's of S. cattleya.Two DHAP dependent aldolases have been identified, one of which is a putative L-fuculose-1-phosphate aldolase which catalyses conversion of 5-FDRibP tofluoroacetaldehyde. The other, an L-fructose 1,6-bisphosphate aldolase has been purifiedto homogeneity and catalyses an aldol reaction between DHAP and fluoroacetaldehyde togenerate 5-FDXyuP. This enzyme is most probably one of primary metabolism.