Identification and metabolism studies of fluorometabolites from different Streptomyces
Abstract
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.
Type
Thesis, PhD Doctor of Philosophy
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