Adenosyl-fluoride synthase

The fluorinase enzyme (, also known as adenosyl-fluoride synthase) catalyzes the reaction between fluoride ion and the co-factor S-adenosyl-L-methionine (SAM) to generate L-methionine and 5'-fluoro-5'-deoxyadenosine, the first committed product of the fluorometabolite biosynthesis pathway. The fluorinase was originally isolated from the soil bacterium Streptomyces cattleya, but homologues have since been identified in a number of other bacterial species, including Streptomyces sp. MA37, Nocardia brasiliensis and Actinoplanes sp. N902-109. This is the only known enzyme capable of catalysing the formation of a carbon-fluorine bond, the strongest single bond in organic chemistry. centre|thumb|upright=3|The fluorinase catalyses the reaction between fluoride ion and the co-factor S-adenosyl-L-methioinine (SAM) to generate 5'-fluoro-5'-deoxyadenosine (FDA) and L-methionine (L-Met).A homologous chlorinase enzyme, which catalyses the same reaction with chloride rather than fluoride ion, has been isolated from Salinospora tropica, from the biosynthetic pathway of salinosporamide A.

== Reactivity == The fluorinase catalyses an SN2-type nucleophilic substitution at the C-5' position of SAM, while L-methionine acts as a neutral leaving group. The fluorinase-catalysed reaction is estimated to be between 106 and 1015 times faster than the uncatalysed reaction, a significant rate enhancement. Despite this, the fluorinase is still regarded as a slow enzyme, with a turnover number (kcat) of 0.06 min−1. The high kinetic barrier to reaction is attributed to the strong solvation of fluoride ion in water, resulting in a high activation energy associated with stripping solvating water molecules from aqueous fluoride ion, converting fluoride into a potent nucleophile within the active site.