Cofactors

There are no Cofactors for this Enzyme

Reaction Mechanism

nicotinate-nucleotide-dimethylbenzimidazole phosphoribosyltransferase By Reference

Nicotinate mononucleotide:5,6- dimethylbenzimidazole (DMB) phosphoribosyltransferase (CobT) is crucial in the synthesis of alpha-ribose-5'-phosphate, a precursor to the lower ligand of colbamin. The biosynthesis of colbamin requires more than 25 committed enzymes, and the biosynthetic pathway has received much interest because of its complexity. Colbamin synthesis is also of interest in evolutionary biology because of its utilisation by early forms of bacteria and Archaea.

The enzyme has also been shown to act on benzimidazole, and the clostridial enzyme acts on adenine to form 7-alpha-D-ribosyladenine 5'-phosphate.




• Summary
• Step 1
• Products

The carboxylate side chain of Glu317 acts as a catalytic base, abstracting the proton of the N3 of DMB, whereupon the N1 atom attacks the C1' carbon of ribose with concerted displacement of the nicotinate ring. This leads to the direct displacement reaction, with a inversion of configuration of the carbon centre.

Catalytic Residues

AA	Uniprot	Uniprot Resid	PDB	PDB Resid
Glu	Q05603	317	1d0s	317
Glu	Q05603	174	1d0s	174

Step Components

overall reactant used, rate-determining step, bimolecular nucleophilic substitution, proton transfer, overall product formed



Step 1.

The N1 of dimethylbenzimidazole initiates a nucleophilic attack on the C1 of the nicotinate D-ribonucleotide in a substitution reaction, eliminating nicotinate.



Products.

The products of the reaction.

View Reaction Mechanisms in M-CSA

Reaction Parameters

• Kinetic Parameters

  Organism	KM Value [mM]	Substrate	Comment
  Salmonella enterica	0.1	beta-nicotinate D-ribonucleotide	mutant G257D, at 37°C
  Sporomusa ovata	3.9	5,6-Dimethylbenzimidazole	pH 9.0, 37°C, wild-type

• Temperature

  There are no reaction parameters information for this Enzyme.

• pH

  Organism	pH Range	Comment
  Propionibacterium freudenreichii subsp. shermanii	7.3 - 9.7	pH 7.3: about 60% of maximum activity, pH 9.7: about 90% of maximum activity

Associated Proteins

Citations

• The coenzyme B₁₂ precursor 5,6-dimethylbenzimidazole is a flavin antagonist in Salmonella.
• Analysis of Akkermansia muciniphila in Mulberry Galacto-Oligosaccharide Medium via Comparative Transcriptomics.
• Structural studies of the phosphoribosyltransferase involved in cobamide biosynthesis in methanogenic archaea and cyanobacteria.
• Acinetobacter baumannii Catabolizes Ethanolamine in the Absence of a Metabolosome and Converts Cobinamide into Adenosylated Cobamides.
• Biosynthesis of Tetrapyrrole Cofactors by Bacterial Community Inhabiting Porphyrine-Containing Shale Rock (Fore-Sudetic Monocline).
• Cobalamin is present in cells of non-tuberculous mycobacteria, but not in Mycobacterium tuberculosis.
• Remarkably coherent population structure for a dominant Antarctic Chlorobium species.
• Sequencing and Analysis of the Genome of Propionibacterium Freudenreichii T82 Strain: Importance for Industry.
• Microbial Cell Factories for Green Production of Vitamins.
• Genetic analysis, nucleotide sequence, and products of two Pseudomonas denitrificans cob genes encoding nicotinate-nucleotide: dimethylbenzimidazole phosphoribosyltransferase and cobalamin (5'-phosphate) synthase.
• A New Class of Phosphoribosyltransferases Involved in Cobamide Biosynthesis Is Found in Methanogenic Archaea and Cyanobacteria.