The UbiX-UbiD system: The biosynthesis and use of prenylated flavin (prFMN)

The UbiX-UbiD system consists of the flavin prenyltransferase UbiX that produces prenylated FMN that serves as the cofactor for the (de)carboxylase UbiD. Recent developments have provided structural insights into the mechanism of both enzymes, detailing unusual chemistry in each case. The proposed reversible 1,3-dipolar cycloaddition between the cofactor and substrate serves as a model to explain many of the key UbiD family features. However, considerable variation exists in the many branches of the UbiD family tree. •The UbiX-UbiD system presents a rich source of novel flavin chemistry.•UbiX is a prenyl transferase generating the prenylated FMN cofactor (prFMN).•Oxidative maturation of prFMN in the UbiD enzyme generates an azomethine ylide.•Cycloaddition between oxidized prFMN and substrate supports (de)carboxylation.