The enzyme catalyses a complex oxygen-dependent conversion of reduced flavin mononucleotide to form 5,6-dimethylbenzimidazole, the lower ligand of vitamin B12. This conversion involves many sequential steps in two distinct stages, and an alloxan intermediate that acts as a proton donor, a proton acceptor, and a hydride acceptor . The C-2 of 5,6-dimethylbenzimidazole is derived from C-1' of the ribityl group of FMNH2 and 2-H from the ribityl 1'-pro-S hydrogen. While D-erythrose 4-phosphate has been shown to be one of the byproducts, the nature of the other product(s) has not been verified yet.
Specify your search results
The enzyme appears in viruses and cellular organisms
intermediate-assisted reaction mechanism in multifunctional catalysis, conversion of FMNH2 to 5,6-dimethylbenzimidazole proceeds via more than 14 steps in two distinct stages, modeling, analysis of crystal structure and geometry optimization, detailed overview
The enzyme catalyses a complex oxygen-dependent conversion of reduced flavin mononucleotide to form 5,6-dimethylbenzimidazole, the lower ligand of vitamin B12. This conversion involves many sequential steps in two distinct stages, and an alloxan intermediate that acts as a proton donor, a proton acceptor, and a hydride acceptor [4]. The C-2 of 5,6-dimethylbenzimidazole is derived from C-1' of the ribityl group of FMNH2 and 2-H from the ribityl 1'-pro-S hydrogen. While D-erythrose 4-phosphate has been shown to be one of the byproducts, the nature of the other product(s) has not been verified yet.
FMNH2 reacts with oxygen to yield flavin hydroperoxide, which then undergoes a ring expansion with loss of a water molecule to produce intermediate A. This disintegrates further as a result of four hydrolysis reactions in which it is attacked by water molecules. The resulting diaminobenzene product undergoes two oxidation reactions, to form 5,6-dimethylbenzimidazole
in the first stage, BluB catalyzes the incorporation of dioxygen, and the fragmentation of the isoalloxazine ring of FMNH2 to form alloxan and the ribityl dimethylphenylenediimine. In the second stage, BluB exploits alloxan as a multifunctional cofactor, such as a proton donor, a proton acceptor, and a hydride acceptor, to catalyze the remaining no fewer than 10 steps of the reaction. The retro-aldol cleavage of the C1'-C2' bond of intermediate ribityl dimethylphenylenediimine is the rate-determining step, active site model of BluB, overview. The highly conserved residue Asp32 plays critical roles in multiple steps of the conversion by serving as a proton acceptor or a proton shuttle, and another conserved residue Ser167 plays its catalytic role mainly in the rate-determining step by stabilizing the protonated retro-aldol precursor. Formation of peroxyflavin intermediate, overview
FMNH2 reacts with oxygen to yield flavin hydroperoxide, which then undergoes a ring expansion with loss of a water molecule to produce intermediate A. This disintegrates further as a result of four hydrolysis reactions in which it is attacked by water molecules. The resulting diaminobenzene product undergoes two oxidation reactions, to form 5,6-dimethylbenzimidazole
a Tn5 insertion mutant is unable to grow in minimal media and fails to establish a symbiosis with alfalfa. Effect can be rescued by addition of vitamin B12 or of 5,6-dimethylbenzimidazole. Mutant does not produce cobalamin unless 5,6-dimethylbenzimidazole is supplied
enzyme deletion mutant is unable to convert Mg-protoporphyrin IX monomethyl ester into protochlorophyllide, mutant starin grows poorly under anoxic photoheterotrophic conditions
the enzyme is involved in production of vitamin B12, a prerequisite for attempts to naturally fortify foods with B12 by microbial fermentation. Active vitamin B12 is distinguished from the pseudovitamin by the presence of 5,6-dimethylbenzimidazole (DMBI) as the lower ligand. Fusion enzyme BluB/CobT2 is efficient in metabolite channeling, and the enzymes' inability to react with adenine, a lower ligand present in the pseudovitamin, reveals a mechanism favoring the production of the active form of the vitamin, requirement of oxygen for DMBI synthesis, since the organism does not synthesize cobalamin. BluB is responsible for the formation of DMBI from FMNH2 in the presence of oxygen, BluB/CobT2 activates DMBI into alpha-RP in the presence of NaMN
the enzyme is involved in production of vitamin B12, a prerequisite for attempts to naturally fortify foods with B12 by microbial fermentation. Active vitamin B12 is distinguished from the pseudovitamin by the presence of 5,6-dimethylbenzimidazole (DMBI) as the lower ligand. Fusion enzyme BluB/CobT2 is efficient in metabolite channeling, and the enzymes' inability to react with adenine, a lower ligand present in the pseudovitamin, reveals a mechanism favoring the production of the active form of the vitamin, requirement of oxygen for DMBI synthesis, since the organism does not synthesize cobalamin. BluB is responsible for the formation of DMBI from FMNH2 in the presence of oxygen, BluB/CobT2 activates DMBI into alpha-RP in the presence of NaMN
gene bluB/cobT2, a natural fusion gene coding for a predicted phosphoribosyltransferase/nitroreductase, sequence comparisons, recombinant expression of HaloTag-tagged enzyme in Escherichia coli strain KRX
HOME
login
history
all enzymes
BRENDA home
History
1.13.11.79 aerobic 5,6-dimethylbenzimidazole synthase
more
top
Information
