Biosynthesis of F0, precursor of the F420 cofactor, requires a unique two radical-SAM domain enzyme and tyrosine as substrate.

Cofactors play key roles in metabolic pathways. Among them F(420) has proved to be a very attractive target for the selective inhibition of archaea and actinobacteria. Its biosynthesis, in a unique manner, involves a key enzyme, F(0)-synthase. This enzyme is a large monomer in actinobacteria, while it is constituted of two subunits in archaea and cyanobacteria. We report here the purification of both types of F(0)-synthase and their in vitro activities. Our study allows us to establish that F(0)-synthase, from both types, uses 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and tyrosine as substrates but not 4-hydroxylphenylpyruvate as previously suggested. Furthermore, our data support the fact that F(0)-synthase generates two 5'-deoxyadenosyl radicals for catalysis which is unprecedented in reaction catalyzed by radical SAM enzymes.