Identification and metabolism studies of fluorometabolites from different Streptomyces
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To date, only five fluorinated natural products have been identified. These were isolated from both plants and bacteria. The bacterium Streptomyces cattleya has the ability to biosynthesise fluoroacetate and 4-fluoro-L-threonine. The first enzyme discovered to be capable of catalysing a C-F bond from fluoride ion, the fluorinase, was identified from S. cattleya in 2002 and is involved in the first step in the biosynthesis of fluorometabolites. The complete metabolic pathway of fluoroacetate and 4-fluoro-L-threonine in S. cattleya was elucidated utilising a variety of different techniques. Recently, genome studies revealed the presence of four new fluorinase enzymes from different bacterial species. Cultures of one of these species, named Streptomyces sp. MA37, showed the production of new unidentified fluorometabolites. Over-expression of the FdrC gene from Streptomyces sp. MA37 was performed, and enzymatic assays of the FdrC enzyme allowed the conversion of 5-fluoro-5-deoxy-ribose to (2R,3S,4S)-5-fluoro-2,3,4- trihydroxypentanoic acid. Identification of (2R,3S,4S)-5-fluoro-2,3,4-trihydroxypentanoic acid as a new fluorometabolite was then confirmed by synthetic synthesis. Nucleocidin, an antibiotic containing fluorine, was isolated in 1957 from the soil bacterium, Streptomyces calvus. Since its isolation, attempts at re-establishing nucleocidin producing cultures have proven unsuccessful. The biosynthesis of nucleocidin involves a C-F bond- forming enzyme unique to Streptomyces calvus. Production of a commercial strain from Pfizer was established and isotopic labelling studies with different labelled glycerols were completed. Pulse feeding experiments with (2R)-[1- ²H₂]-glycerol, (2S)-[1- ²H₂]-glycerol, glycerol-1,1,2,3,3-d₅ and [2-¹³ C]-glycerol proved to be successful. Concomitantly, synthesis of highly pure putative substrates for the fluorinating enzyme was carried out. Unfortunately, cell-free extract experiments were achieved, but results from these were not conclusive.
Thesis, PhD Doctor of Philosophy
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