Recombinant Nitrosomonas europaea 6,7-dimethyl-8-ribityllumazine synthase (ribH)
Description
Kinetic Properties and Substrate Binding
Recombinant RibH enzymes exhibit distinct kinetic parameters across species:
| Organism | Vₘₐₓ (nmol·mg⁻¹·h⁻¹) | Kₘ (Substrate 1, μM) | Kₘ (Substrate 2, μM) | Reference |
|---|---|---|---|---|
| Schizosaccharomyces pombe | 13,000 | 5 | 67 | |
| Brucella abortus (Type I) | 1,080 | 125* | N/A |
*Substrate 1: 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione; Substrate 2: 3,4-dihydroxy-2-butanone 4-phosphate.
*Reported as K value for 3,4-dihydroxy-2-butanone 4-phosphate in Brucella .
Biotechnological and Metabolic Relevance
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Riboflavin Biosynthesis: RibH is essential for flavin cofactor production, which supports electron transport in N. europaea’s ammonia monooxygenase and hydroxylamine oxidoreductase .
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Structural Insights: X-ray crystallography of homologs (e.g., PDB 2A58) reveals a β-barrel fold with active sites stabilized by hydrophobic residues . Trp27 in S. pombe forms a π-complex with riboflavin, a feature likely conserved in bacterial homologs .
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Bioremediation Potential: While N. europaea is noted for degrading halogenated organics , RibH’s role in secondary metabolism remains unexplored.
Research Gaps and Future Directions
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Gene Localization: Is ribH part of an operon or regulated independently?
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Catalytic Efficiency: How do kinetic parameters compare to homologs?
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Structural Data: High-resolution structures of N. europaea RibH are lacking.
Comparative Analysis with Homologs
| Feature | Nitrosomonas europaea (Inferred) | Brucella abortus (Type I) | Schizosaccharomyces pombe |
|---|---|---|---|
| Quaternary Structure | Likely pentameric | Pentameric | Pentameric |
| Kₘ (Substrate 1) | Undetermined | N/A | 5 μM |
| Role in Metabolism | Flavin cofactor synthesis | Flavin synthesis, virulence | Riboflavin production |
Product Specs
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Target Background
Function: Catalyzes the condensation of 5-amino-6-(D-ribitylamino)uracil and 3,4-dihydroxy-2-butanone 4-phosphate to form 6,7-dimethyl-8-ribityllumazine. This reaction represents the penultimate step in riboflavin biosynthesis.
KEGG: neu:NE2557
STRING: 228410.NE2557
