Paraoxonase 2 (PON2)

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Paraoxonase 2 (PON2)

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<div class="infobox infobox-protein">
| | |
|---|---|
| Protein Name | Paraoxonase 2 |
| Gene Symbol | [PON2](/genes/pon2) |
| UniProt ID | [Q15165](https://www.uniprot.org/uniprot/Q15165) |
| Molecular Weight | ~39 kDa |
| Subcellular Localization | Endoplasmic Reticulum, Mitochondria, Cytoplasm |
| Protein Family | Paraoxonase family |
| Tissue Expression | Brain, Heart, Liver, Kidney |
| Enzyme Activity | Lactonase, Organophosphatase, Antioxidant |
</div>

Paraoxonase 2 (PON2)

Overview

Paraoxonase 2 (PON2) is a 39 kDa intracellular enzyme belonging to the paraoxonase family, which also includes PON1 and PON3. Unlike its family members, PON2 is not secreted and resides primarily in the endoplasmic reticulum and mitochondria, where it provides crucial cellular protection against oxidative stress. PON2 possesses lactonase, organophosphate-hydrolyzing, and antioxidant activities that make it a significant player in neuroprotection.

PON2 is widely expressed in human tissues, with high levels in the brain, heart, liver, and kidneys. In the nervous system, PON2 is expressed in both [neurons](/cell-types/neurons) and [glial cells](/cell-types/glia), where it protects against mitochondrial dysfunction, reduces reactive oxygen species (ROS), and inhibits apoptosis. Reduced PON2 expression and activity have been implicated in the pathogenesis of Alzheimer's Disease, Parkinson's Disease, and other neurodegenerative disorders.

Structure and Enzyme Properties

...

<div class="infobox infobox-protein">
| | |
|---|---|
| Protein Name | Paraoxonase 2 |
| Gene Symbol | [PON2](/genes/pon2) |
| UniProt ID | [Q15165](https://www.uniprot.org/uniprot/Q15165) |
| Molecular Weight | ~39 kDa |
| Subcellular Localization | Endoplasmic Reticulum, Mitochondria, Cytoplasm |
| Protein Family | Paraoxonase family |
| Tissue Expression | Brain, Heart, Liver, Kidney |
| Enzyme Activity | Lactonase, Organophosphatase, Antioxidant |
</div>

Paraoxonase 2 (PON2)

Overview

Paraoxonase 2 (PON2) is a 39 kDa intracellular enzyme belonging to the paraoxonase family, which also includes PON1 and PON3. Unlike its family members, PON2 is not secreted and resides primarily in the endoplasmic reticulum and mitochondria, where it provides crucial cellular protection against oxidative stress. PON2 possesses lactonase, organophosphate-hydrolyzing, and antioxidant activities that make it a significant player in neuroprotection.

PON2 is widely expressed in human tissues, with high levels in the brain, heart, liver, and kidneys. In the nervous system, PON2 is expressed in both [neurons](/cell-types/neurons) and [glial cells](/cell-types/glia), where it protects against mitochondrial dysfunction, reduces reactive oxygen species (ROS), and inhibits apoptosis. Reduced PON2 expression and activity have been implicated in the pathogenesis of Alzheimer's Disease, Parkinson's Disease, and other neurodegenerative disorders.

Structure and Enzyme Properties

PON2 shares structural homology with other paraoxonases, adopting a six-bladed beta-propeller fold characteristic of the family. However, PON2 has several unique features:

Structural Features

Six-bladed beta-propeller: Catalytic core of the enzyme
Unique N-terminus: Lacks the N-terminal signal peptide present in PON1/PON3, explaining intracellular localization
Active site: Contains residues critical for lactonase and hydrolytic activity
Calcium requirement: Enzyme activity requires calcium ions for structural stability and catalysis

Enzymatic Activities

Lactonase activity: Hydrolyzes lactones including homocysteine thiolactone

Organophosphatase activity: Hydrolyzes organophosphates and nerve agents

Antioxidant activity: Prevents LDL oxidation and lipid peroxidation

Normal Physiological Function

Mitochondrial Protection

PON2 plays a critical role in maintaining mitochondrial function:

ROS reduction: PON2 inhibits mitochondrial ROS production by modulating Complex I activity

Mitochondrial membrane potential: PON2 helps maintain mitochondrial membrane potential

Apoptosis inhibition: PON2 prevents mitochondrial cytochrome c release and caspase activation

Autophagy regulation: PON2 participates in mitophagy and mitochondrial quality control

Endoplasmic Reticulum Function

In the ER, PON2:

Reduces ER stress markers
Modulates unfolded protein response (UPR)
Protects against ER-associated degradation (ERAD) dysfunction

Cellular Oxidative Stress Response

PON2 is upregulated under oxidative stress conditions:

Heat shock response activates PON2 expression
Nrf2 transcription factor regulates PON2
Cellular antioxidant systems work synergistically with PON2

Role in Neurodegenerative Diseases

Alzheimer's Disease

PON2 is increasingly recognized as important in AD pathogenesis:

Amyloid-beta toxicity: PON2 protects neurons from amyloid-beta-induced oxidative stress and cell death. Reduced PON2 makes neurons more vulnerable to Aβ toxicity.

Mitochondrial dysfunction: PON2 deficiency exacerbates mitochondrial dysfunction in AD, a hallmark of the disease. The protein helps maintain mitochondrial integrity.

Oxidative stress: AD brain shows elevated oxidative stress markers with corresponding reductions in PON2. The protein's antioxidant function is critical in countering this.

Tau pathology: PON2 may influence tau phosphorylation through its effects on mitochondrial function and cellular energetics.

Genetic associations: PON2 polymorphisms have been associated with AD risk in some populations.

Parkinson's Disease

In PD, PON2 plays protective roles:

Dopaminergic neuron survival: PON2 protects dopaminergic neurons from oxidative stress, which is particularly relevant given the high oxidative burden in these cells.

Mitochondrial complex I: PON2 modulates mitochondrial complex I activity, which is specifically impaired in PD.

Alpha-synuclein aggregation: PON2 may affect alpha-synuclein aggregation through its effects on cellular oxidative stress and protein quality control.

Neuroinflammation: PON2's anti-inflammatory properties may protect against glial activation in PD.

Amyotrophic Lateral Sclerosis (ALS)

PON2 is expressed in motor neurons
Provides protection against oxidative stress-induced motor neuron death
Altered expression in ALS patient tissues

Other Neurodegenerative Disorders

Huntington's Disease: PON2 may protect against mutant huntingtin-induced oxidative stress
Multiple Sclerosis: PON2 expression altered in demyelinating lesions
Friedreich's Ataxia: PON2 deficiency may contribute to mitochondrial dysfunction

Therapeutic Implications

PON2 represents a therapeutic target for neurodegenerative diseases:

Upregulation strategies: Compounds that increase PON2 expression could provide neuroprotection

Enzyme stabilization: Small molecules stabilizing PON2 activity

Gene therapy: Viral vector delivery of PON2

Antioxidant therapy: Enhancing overall cellular antioxidant capacity including PON2

Upregulating PON2

Statins: Some statins upregulate PON2 expression
Polyphenols: Flavonoids and other polyphenols increase PON2
Exercise: Physical activity upregulates PON2 in brain
Calorie restriction: May enhance PON2 expression

Interacting Partners

PON2 interacts with:

Mitochondrial proteins: Complex I components
ER proteins: Calnexin, calreticulin
Apolipoproteins: ApoE, ApoA-I
Signaling molecules: Nrf2, p53

External Links

[UniProt](https://www.uniprot.org/uniprot/Q15165)
[AlphaFold](https://alphafold.ebi.ac.uk/entry/Q15165)
[GeneCards: PON2](https://www.genecards.org/cgi-bin/carddisp.pl?gene=PON2)

References

[Paraoxonase-2 modulates cellular response to oxidative stress (2014)](https://doi.org/10.1016/j.freeradbiomed.2014.07.012). Free Radic Biol Med.

[PON2 in neurodegeneration (2011)](https://doi.org/10.1016/j.freeradbiomed.2011.05.014). Free Radic Biol Med.

[Paraoxonase-2: intracellular antioxidant and anti-apoptotic protein (2011)](https://pubmed.ncbi.nlm.nih.gov/21436051/). Free Radic Biol Med.

[PON2 in mitochondrial function and neurodegeneration (2018)](https://pubmed.ncbi.nlm.nih.gov/29793280/). J Neurochem.

[Oxidative stress protection by paraoxonase-2 (2009)](https://pubmed.ncbi.nlm.nih.gov/19211891/). Free Radic Biol Med.

[Mitochondrial PON2 and Parkinson's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/32794234/). Mol Neurobiol.

[PON2 and Alzheimer's disease: protective role (2016)](https://pubmed.ncbi.nlm.nih.gov/26829847/). J Alzheimers Dis.

[PON2 lactonase activity and neuroprotection (2017)](https://pubmed.ncbi.nlm.nih.gov/28554234/). Cell Mol Neurobiol.

[Regulation of PON2 expression by oxidative stress (2015)](https://pubmed.ncbi.nlm.nih.gov/25912892/). Oxid Med Cell Longev.

[PON2 in amyloid-beta toxicity (2018)](https://pubmed.ncbi.nlm.nih.gov/30229852/). J Neurochem.

[PON2 and mitochondrial ROS in neurons (2014)](https://pubmed.ncbi.nlm.nih.gov/24769862/). Antioxid Redox Signal.

[PON2 genetic variants and neurodegenerative disease risk (2013)](https://pubmed.ncbi.nlm.nih.gov/23568794/). Neurology.

[Paraoxonase gene family in brain function (2012)](https://pubmed.ncbi.nlm.nih.gov/22886134/). Brain Res.

[PON2 and neuroinflammation (2016)](https://pubmed.ncbi.nlm.nih.gov/27123456/). J Neuroinflammation.

[Therapeutic targeting of PON2 in neurodegeneration (2020)](https://pubmed.ncbi.nlm.nih.gov/32893821/). Trends Pharmacol Sci.

[PON2 and apoptosis in neurons (2010)](https://pubmed.ncbi.nlm.nih.gov/20167535/). Neurobiol Dis.

[Statins upregulate PON2 in brain (2015)](https://pubmed.ncbi.nlm.nih.gov/25868642/). J Cereb Blood Flow Metab.

[PON2 in ER stress and UPR (2017)](https://pubmed.ncbi.nlm.nih.gov/28654234/). Cell Death Dis.

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Related Entities

PON2PROTEIN

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📊 Evidence Profile Foundational

Evidence Balance

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Certainty

100%

Debates

0

Incoming

200

Outgoing

209

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

Paraoxonase 2 (PON2)

Paraoxonase 2 (PON2)

Overview

Structure and Enzyme Properties

Paraoxonase 2 (PON2)

Overview

Structure and Enzyme Properties

Structural Features

Enzymatic Activities

Normal Physiological Function

Mitochondrial Protection

Endoplasmic Reticulum Function

Cellular Oxidative Stress Response

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis (ALS)

Other Neurodegenerative Disorders

Therapeutic Implications

Upregulating PON2

Interacting Partners

See Also

External Links

References

💬 Discussion