ID 1.13.11.79 DE aerobic 5,6-dimethylbenzimidazole synthase. AN flavin reductase. CA FMNH2 + O2 = 5,6-dimethylbenzimidazole + D-erythrose 4-phosphate + CA dialurate + H(+). CC -!- The enzyme catalyzes a complex oxygen-dependent conversion of reduced CC flavin mononucleotide to form 5,6-dimethylbenzimidazole, the lower CC ligand of vitamin B12. CC -!- This conversion involves many sequential steps in two distinct CC stages, and an alloxan intermediate that acts as a proton donor, CC a proton acceptor, and a hydride acceptor. CC -!- The C-2 of 5,6-dimethylbenzimidazole is derived from C-1' of the CC ribityl group of FMNH2 and 2-H from the ribityl 1'-pro-S hydrogen. CC -!- While D-erythrose 4-phosphate has been shown to be one of the CC by-products, the nature of the other product(s) has not been verified CC yet. CC -!- Formerly EC 1.14.99.40. DR Q92PC8, BLUB_RHIME ; P0CY55, BLUB_RHOCA ; D5AV14, BLUB_RHOCB ; DR Q2RNG5, BLUB_RHORT ; //