InterPro domain: IPR000422

3,4-dihydroxy-2-butanone 4-phosphate synthase ( 4.1.99.12 ) (DHBP synthase) (RibB) catalyses the conversion of D-ribulose 5-phosphate to formate and 3,4-dihydroxy-2-butanone 4-phosphate, the latter serving as the biosynthetic precursor for the xylene ring of riboflavin [ 1 ]. In Photobacterium leiognathi, the riboflavin synthesis genes ribB (DHBP synthase), ribE (riboflavin synthase), ribH (lumazone synthase) and ribA (GTP cyclohydrolase II) all reside in the lux operon [ 2 ]. RibB is sometimes found as a bifunctional enzyme with GTP cyclohydrolase II that catalyses the first committed step in the biosynthesis of riboflavin ( IPR000926 ). No sequences with significant homology to DHBP synthase are found in the metazoa.

1. Biosynthesis of riboflavin: 3,4-dihydroxy-2-butanone-4-phosphate synthase. Meth. Enzymol. 280, 374-82
2. Riboflavin synthesis genes ribE, ribB, ribH, ribA reside in the lux operon of Photobacterium leiognathi. Biochem. Biophys. Res. Commun. 284, 587-95