Recombinant Human Lysoplasmalogenase (TMEM86B)
Description
Molecular Characterization
TMEM86B encodes a 19 kDa hydrophobic transmembrane protein belonging to the YhhN family . Structural features include:
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Catalytic residues: Asp82 and Asp190, essential for enzymatic activity
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Specificity: Exclusively targets sn-2-deacylated lysoplasmalogens (not intact plasmalogens)
A comparative analysis of enzymatic properties is shown below:
| Parameter | Lysoplasmenylcholine | Lysoplasmenylethanolamine |
|---|---|---|
| Apparent (μM) | ~50 | ~50 |
| Apparent | 24.5 μmol/min/mg | 17.5 μmol/min/mg |
| pH Optimum | 7.0 | 7.0 |
| Inhibitor (Competitive) | Lysophosphatidic acid () |
Functional Roles in Lipid Metabolism
Recombinant TMEM86B has been instrumental in elucidating:
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Plasmalogen regulation: Overexpression in HEK 293T cells reduces cellular plasmalogen levels by 30–40%, confirming its role in lipid homeostasis .
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Membrane stability: Hydrolyzes cytotoxic lysoplasmalogens, preventing membrane disruption .
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Disease links: Associated with peroxisomal disorders (e.g., rhizomelic chondrodysplasia punctata) and neurodegenerative conditions .
Recombinant Production Systems
TMEM86B has been expressed in multiple systems:
Mechanistic Insights
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Substrate preference: Hydrolyzes both choline- and ethanolamine-linked lysoplasmalogens .
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Metabolic impact: Knockout studies in adipocytes show increased lysoplasmalogen levels and enhanced cAMP/PKA signaling .
Disease Relevance
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Neurodegeneration: Reduced plasmalogen levels in Alzheimer’s disease correlate with upregulated TMEM86B activity .
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Cancer: Elevated lysoplasmalogenase activity observed in tumor cell lines .
Research Applications
Product Specs
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Generally, the shelf life of the liquid form is 6 months at -20°C/-80°C, while the lyophilized form has a shelf life of 12 months at -20°C/-80°C.
Target Background
- Transient transfection of human embryonic kidney (HEK) 293T cells with TMEM86b cDNA demonstrated lysoplasmalogenase activity. Western blot analysis confirmed the synthesis of TMEM86b protein PMID: 21515882
Q&A
Basic Research Questions
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What is the biochemical function of human lysoplasmalogenase (TMEM86B)?
Human lysoplasmalogenase (TMEM86B) catalyzes the hydrolytic cleavage of the vinyl ether bond of lysoplasmalogen, forming a fatty aldehyde and either glycerophosphoethanolamine or glycerophosphocholine. The enzyme is specific for the sn-2-deacylated form of plasmalogen and plays a crucial role in regulating plasmalogen levels in cells. Biochemical characterization has shown that TMEM86B has apparent Km values of approximately 50 μM for both lysoplasmenylcholine and lysoplasmenylethanolamine substrates, with Vmax values of 24.5 and 17.5 μmol/min/mg protein, respectively . Overexpression studies have demonstrated that TMEM86B can decrease cellular plasmalogen levels, highlighting its importance in lipid homeostasis .
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How does TMEM86B differ structurally and functionally from TMEM86A?
Both TMEM86A and TMEM86B belong to the YhhN family of proteins and possess lysoplasmalogenase activity, but they differ in tissue distribution and potentially in substrate specificity. TMEM86B is predominantly expressed in the liver, whereas TMEM86A is enriched in adipocytes . Structurally, both proteins are predicted to have multiple transmembrane regions and share evolutionarily conserved catalytic residues. In TMEM86A, aspartate residues D82 and D190 have been identified as critical for catalytic activity . AlphaFold computational modeling predicts that TMEM86A contains 8 transmembrane regions, and by homology, TMEM86B likely has a similar structure . Functionally, TMEM86A has been implicated in adipocyte metabolism and energy homeostasis, with its deletion protecting mice from obesity and insulin resistance .
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What are the optimal conditions for assessing recombinant TMEM86B enzymatic activity?
Recombinant TMEM86B exhibits optimal enzymatic activity at pH 7.0 . For in vitro assays, the enzyme requires appropriate detergent conditions for solubilization while maintaining activity, with octyl glucoside being successfully employed for this purpose . Two primary methodological approaches can be used to assess activity:
Method Applications Key Considerations Spectrophotometric coupled assay Routine activity measurements Links aldehydes formed to NAD+ reduction by alcohol dehydrogenase Two-dimensional TLC Stoichiometric studies, inhibitor assessments Can track changes in substrate and multiple products simultaneously The enzyme is competitively inhibited by lysophosphatidic acid with a Ki of approximately 20 μM, which should be considered when designing experimental conditions . No cofactors appear necessary for activity.
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Which expression systems are suitable for producing recombinant human TMEM86B?
Recombinant TMEM86B has been successfully expressed in multiple systems:
Expression System Advantages Considerations HEK293T cells Proper post-translational modifications Requires optimization of transfection methods E. coli Higher yield potential, cost-effective May require refolding strategies for functional protein For mammalian expression, transient transfection with appropriate vectors containing TMEM86B cDNA can be employed . In both systems, expression verification should include Western blot analysis and activity assays. When designing expression constructs, consideration should be given to the addition of purification tags (His, FLAG) that do not interfere with enzymatic function. Since TMEM86B is a membrane protein, optimization of solubilization and purification protocols is essential for obtaining active enzyme .
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What is the subcellular localization of TMEM86B and how can it be studied?
TMEM86B is predominantly localized to membrane fractions of cells, specifically in the endoplasmic reticulum (ER) membrane . This localization aligns with its function in lipid metabolism, as the ER is a major site for phospholipid synthesis and metabolism. By analogy with TMEM86A, which strongly colocalizes with ER Tracker staining in cells, TMEM86B likely exhibits similar localization patterns .
Methodological approaches for studying TMEM86B localization include:
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Subcellular fractionation followed by Western blotting
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Immunofluorescence microscopy using TMEM86B-specific antibodies
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Expression of fluorescently tagged TMEM86B (e.g., GFP-TMEM86B) with live-cell imaging
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Co-localization studies with established ER markers (calnexin, PDI)
When interpreting localization data, consideration should be given to potential artifacts from overexpression systems versus endogenous protein detection.
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