FMN and FAD are prosthetic groups of many enzymes and can be attached to proteins both covalently and non-covalently. Covalent attachment of FMN to Thr or Ser residues via a phosphate group is catalyzed by the recently discovered enzyme flavin transferase. Among the enzymes containing phosphoester-linked FMN, the most widely represented are various microbial 2-enoate reductases catalyzing the reduction of unsaturated carboxylic acids such as fumaric, acrylic, cinnamic, urocanic, and others. This review is focused on these enzymes and discusses their types by domain organization and intracellular localization, structural basis of substrate specificity, catalytic mechanism, role, as well as the significance and evolutionary origin of the covalent attachment of FMN as a prosthetic group.
Bogachev et al. (Wed,) studied this question.