Enzymatic fluorination in Streptomyces cattleya takes place with an inversion of configuration consistent with an SN2 reaction mechanism

The stereochemical course of the recently isolated fluorination enzyme from Streptomyces cattleya has been evaluated. The enzyme mediates a reaction between fluoride ion and S-adenosyl-L-methionine (SAM) to generate 5'-fluoro-5'-deoxy-adenosine (5'-FDA). Preparation of (5'R)-[5-H-2(1)]-ATP generated (5'-R)-[5-H-2(1)]-5'-FDA in a coupled enzyme assay involving SAM synthase and the fluorinase. The stereochemical analysis of the product relied on H-2 NMR analysis in a chiral liquid-crystalline medium. It is concluded that the enzyme catalyses the fluorination with an inversion of configuration consistent with an S(N)2 reaction mechanism.