5-[18F]Fluoro-5-deoxyribose ([18F]FDR) is a novel monosaccharide radiotracer produced by a two-enzyme biotransformation, at the John Mallard Scottish PET Centre in Aberdeen, UK. The two-step process uses fluorinase, a C-F bond forming enzyme, and a nucleoside hydrolase. In the first step, S-adenosyl-L-methionine (SAM) and [18F]-fluoride are incubated with the fluorinase enzyme. The product of this reaction, [18F]-5′-fluoro-5′-deoxadenosine ([18F]FDA) is incubated with an adenosine hydrolase to generate [18F]FDR. The enzymes were produced and freeze-dried by the O’Hagan group at St Andrews University, and were used on demand by dissolution in water.