RPIA Human
Description
Overview of RPIA Human
RPIA (EC 5.3.1.6) catalyzes the reversible isomerization of ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P), a key step in the PPP. This pathway generates NADPH for biosynthetic processes and ribose precursors for nucleotide synthesis . Structurally, RPIA is conserved across eukaryotes and exists as a homodimer with subunits of ~25 kDa . The human RPIA gene is located on chromosome 2p11.2 and spans ~60,000 base pairs .
Functional Roles in Metabolic Pathways
RPIA operates in two major pathways:
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Pentose Phosphate Pathway (PPP):
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Calvin Cycle (Plants):
Metabolic Implications:
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Cancer: RPIA overexpression in hepatocellular carcinoma (HCC) correlates with tumor size, stage, and ERK/PP2A signaling dysregulation .
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Malaria: Plasmodium falciparum relies on RPIA for NADPH and nucleic acid synthesis, highlighting it as a therapeutic target .
A. RPIA Deficiency
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A rare genetic disorder caused by RPIA mutations (e.g., premature stop codons or missense variants) .
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Symptoms: Developmental delay, leukoencephalopathy, epilepsy, and abnormal polyol metabolism .
B. Oncogenic Role
A. Recombinant RPIA Proteins
B. Diagnostic Kits
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Human RPIA ELISA Kit: Detects RPIA in serum/plasma (sensitivity: 0.938 ng/ml; range: 1.56–100 ng/ml) .
Recent Research Advancements
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HCC Pathogenesis:
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Therapeutic Targeting:
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Digital Twin Systems:
Future Directions
Product Specs
Q&A
What is the biochemical role of RPIA in the pentose phosphate pathway?
RPIA catalyzes the interconversion of ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P), a critical step in the non-oxidative phase of the pentose phosphate pathway (PPP). This reaction enables the synthesis of nucleotide precursors and NADPH, essential for redox homeostasis . Methodological confirmation involves:
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Enzyme activity assays: Spectrophotometric quantification of substrate depletion (R5P) and product formation (Ru5P) under controlled pH and temperature .
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Isotopic tracing: Using -labeled glucose to track carbon flux through the PPP in RPIA-deficient cell lines .
How is RPIA deficiency diagnostically confirmed in patients?
RPIA deficiency (OMIM #608611) is identified through a multi-modal approach:
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Urinary polyol profiling: Elevated arabitol and ribitol via gas chromatography-mass spectrometry (GC-MS) .
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Genetic sequencing: Whole-exome screening for pathogenic variants in RPIA (e.g., c.770T>C p.Ile257Thr) .
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Neuroimaging: MRI detection of leukoencephalopathy and white matter abnormalities .
What cellular models are used to study RPIA dysfunction?
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Fibroblast cultures: Derived from patients with confirmed RPIA mutations to assess PPP metabolite accumulation (e.g., R5P/Ru5P ratios via HPLC) .
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CRISPR-Cas9 knockouts: HEK293T cells with RPIA deletions to study compensatory pathways like the hexose monophosphate shunt .
How do researchers resolve contradictions in reported RPIA activity levels across studies?
Discrepancies often arise from methodological variability, addressed through:
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Standardized assay conditions: Buffer pH (7.4 vs. 7.8) alters isomerization rates; optimal activity occurs at 37°C with 2 mM Mg .
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Normalization protocols: Activity expressed per mg protein (Bradford assay) rather than total cell lysate .
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Inter-laboratory validation: Collaborative trials using shared reference samples (NIST-certified R5P) .
What experimental designs control for confounding variables in RPIA knockout studies?
To isolate RPIA-specific effects:
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ShRNA controls: Non-targeting vectors account for off-target RNA interference .
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Isogenic cell lines: Wild-type vs. mutant RPIA clones generated via homologous recombination .
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Metabolic rescue experiments: Supplementation with R5P or NADPH precursors (e.g., nicotinamide riboside) .
How can multi-omics datasets clarify RPIA’s role in neurodegeneration?
Integrative analysis strategies include:
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Transcriptomic profiling: RNA-seq of patient-derived neurons to identify dysregulated pathways (e.g., oxidative stress response genes) .
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Metabolomic networks: Weighted correlation of PPP intermediates with CSF biomarkers (GFAP, neurofilament light chain) .
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Structural modeling: AlphaFold2-predicted RPIA mutants (e.g., Ile257Thr) to map destabilizing effects on substrate binding .
Methodological Comparison Table
Data Contradiction Analysis Framework
Case Study: Conflicting reports on R5P accumulation in RPIA-deficient models.
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Hypothesis Testing:
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Null hypothesis: R5P elevation is invariant across tissue types.
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Alternative hypothesis: Compartment-specific PPP activity modulates R5P levels.
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Experimental Replication:
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Statistical Reconciliation:
Emerging Research Directions
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Gene therapy vectors: AAV9-mediated RPIA delivery in murine models of leukoencephalopathy .
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Small molecule activators: High-throughput screening of 50,000 compounds for RPIA enhancers (Z’ factor >0.5) .
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Cryo-EM structural studies: 3.2 Å resolution maps of RPIA-ribitol complexes to guide inhibitor design .
Product Science Overview
Ribose 5-Phosphate Isomerase A (RPIA) is an enzyme encoded by the RPIA gene in humans. This enzyme plays a crucial role in the pentose phosphate pathway, which is essential for cellular metabolism. The enzyme catalyzes the reversible conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P), facilitating the interconversion of these structural isomers of pentose .
The RPIA gene is located on the short arm (p arm) of the second chromosome at position 11.2. The gene spans nearly 60,000 base pairs and encodes a protein that forms a homodimer consisting of two 25 kDa subunits . The molecular mass of the RPIA dimer is approximately 49 kDa . The enzyme’s structure includes a five-stranded β-sheet surrounded by α-helices, forming an αβα motif .
RPIA is highly conserved across various species, indicating its ancient origins and essential role in metabolism. Knock-out experiments on genes encoding RPIA in different species have shown similar conserved residues and structural motifs . This conservation suggests that the enzyme has been present throughout most of evolutionary history .
RPIA is involved in the pentose phosphate pathway, a metabolic pathway parallel to glycolysis. This pathway generates NADPH and pentoses (5-carbon sugars) as well as ribose-5-phosphate for nucleotide synthesis. The enzyme’s activity is crucial for maintaining cellular redox balance and providing precursors for biosynthetic processes .
RPIA has garnered attention as a potential drug target for treating diseases caused by trypanosomatid parasites, such as Chagas’ disease, leishmaniasis, and human African trypanosomiasis . Additionally, the enzyme’s role in the pentose phosphate pathway makes it a valuable biocatalyst for producing rare sugars, including D-allose, L-rhamnulose, L-lyxose, and L-tagatose .
