Recombinant Photobacterium profundum Pyrimidine-specific ribonucleoside hydrolase RihA (rihA)
Description
Enzymatic Function and Substrate Specificity
RihA belongs to the ribonucleoside hydrolase (Rih) family, which cleaves the N-glycosidic bond of ribonucleosides. Pyrimidine-specific hydrolases like RihA preferentially act on cytidine and uridine, producing cytosine/uracil and ribose . In E. coli, RihA operates in parallel with phosphorolytic pathways but is nonessential under standard conditions . Homologs in P. profundum likely share this substrate specificity, though experimental validation is pending.
Key Reaction
2.1. Gene Organization
In E. coli, rihA (formerly ybeK) is part of a trio of hydrolase genes (rihA, rihB, rihC) . While P. profundum genome annotations do not explicitly mention rihA, genomic islands in this species (e.g., fatty acid biosynthesis clusters on chromosome 2) suggest metabolic redundancy and adaptability . Homology searches indicate conserved domains for nucleoside metabolism, though direct evidence for rihA remains uncharacterized.
2.2. Regulation
In E. coli, rihA expression is suppressed under glucose-rich conditions due to catabolite repression . Similar regulatory mechanisms may exist in P. profundum, given its metabolic flexibility in deep-sea environments .
3.2. Kinetic Parameters (Inferred from E. coli RihA)
| Substrate | (μM) | (s) | (Ms) |
|---|---|---|---|
| Cytidine | 58.6 | 2.0 | 3.4 × 10 |
| Uridine | 45.2 | 1.8 | 4.0 × 10 |
| Data adapted from E. coli RihA studies . |
4.1. Metabolic Salvage Pathways
In E. coli, RihA enables pyrimidine salvage in cdd mutants lacking cytidine deaminase . For P. profundum, which inhabits high-pressure marine environments, RihA might complement nucleoside phosphorylases under nutrient-limited conditions or stress . Its role could overlap with polyunsaturated fatty acid (PUFA) biosynthesis pathways, which are critical for membrane adaptation .
4.2. Stress Response
Genomic studies of P. profundum highlight upregulated small RNAs (sRNAs) and extended 5'-UTRs under high hydrostatic pressure . While no direct link to rihA exists, such regulatory elements could modulate hydrolase activity during environmental stress.
5.1. Enzyme Engineering
RihA’s substrate specificity makes it a candidate for enzymatic synthesis of nucleobases or ribose derivatives. Directed evolution could enhance its stability for industrial processes .
5.2. Drug Design
Protozoan Rih homologs are drug targets due to their essentiality in purine-pyrimidine salvage . Although P. profundum RihA is nonpathogenic, its structural insights could inform inhibitor design for parasitic enzymes.
Research Gaps and Future Directions
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Functional Characterization: Heterologous expression and kinetic assays are needed to confirm P. profundum RihA activity.
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Genomic Context: Linkage to adjacent genes (e.g., ribEBHA in E. coli) could reveal operon-level regulation .
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Environmental Adaptations: Pressure-responsive expression studies would clarify RihA’s role in deep-sea niches .
Product Specs
Note: We will prioritize shipping the format currently in stock. However, if you have a specific format requirement, please indicate it during order placement. We will fulfill your request based on availability.
Note: All protein shipments are sent with standard blue ice packs. If you require dry ice shipment, please communicate with us in advance as additional fees will apply.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. The shelf life of lyophilized form is 12 months at -20°C/-80°C.
Target Background
KEGG: ppr:PBPRA2062
STRING: 298386.PBPRA2062
