The enzyme catalyses the transfer of the FMN portion of FAD and its covalent binding to the hydroxyl group of an L-threonine residue in a target flavin-binding protein such as the B and C subunits of EC 126.96.36.199, NADH:ubiquinone reductase (Na+-transporting). Requires Mg2+.
Bertsova, Y.V., Fadeeva, M.S., Kostyrko, V.A., Serebryakova, M.V., Baykov, A.A. and Bogachev, A.V. Alternative pyrimidine biosynthesis protein ApbE is a flavin transferase catalyzing covalent attachment of FMN to a threonine residue in bacterial flavoproteins. J. Biol. Chem.288 (2013) 14276–14286. [PMID: 23558683]