KYAT3 Protein

KYAT3 Protein

Introduction

Kyat3 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@potter2010]
<table> [@schwarcz2012]
<tr><th colspan="2">KYAT3 Protein</th></tr> [@haroutunian2015]
<tr><td>Protein Name</td><td>Kynurenine Aminotransferase 3</td></tr> [@zdori2019]
<tr><td>Gene</td><td>[KYAT3](/genes/kyat3)</td></tr>
<tr><td>UniProt</td><td>[Q9H3R9](https://www.uniprot.org/uniprot/Q9H3R9)</td></tr>
<tr><td>Molecular Weight</td><td>45 kDa</td></tr>
<tr><td>Subcellular Localization</td><td>Cytoplasm, Mitochondria</td></tr>
<tr><td>Protein Family</td><td>Aminotransferase family (fold class I)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

KYAT3 (Kynurenine Aminotransferase 3), also known as KAT3 or CCBL2 (Cysteine Conjugate-Beta Lyase 2), is a pyridoxal phosphate-dependent aminotransferase involved in the kynurenine pathway of tryptophan degradation. This pathway produces neuroactive metabolites including kynurenic acid and quinolinic acid, which have opposing effects on [NMDA](/entities/nmda-receptor) receptor signaling. KYAT3 is implicated in epilepsy, Alzheimer's disease, and Parkinson's disease^[1].

Structure

...

KYAT3 Protein

Introduction

Kyat3 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@potter2010]
<table> [@schwarcz2012]
<tr><th colspan="2">KYAT3 Protein</th></tr> [@haroutunian2015]
<tr><td>Protein Name</td><td>Kynurenine Aminotransferase 3</td></tr> [@zdori2019]
<tr><td>Gene</td><td>[KYAT3](/genes/kyat3)</td></tr>
<tr><td>UniProt</td><td>[Q9H3R9](https://www.uniprot.org/uniprot/Q9H3R9)</td></tr>
<tr><td>Molecular Weight</td><td>45 kDa</td></tr>
<tr><td>Subcellular Localization</td><td>Cytoplasm, Mitochondria</td></tr>
<tr><td>Protein Family</td><td>Aminotransferase family (fold class I)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

KYAT3 (Kynurenine Aminotransferase 3), also known as KAT3 or CCBL2 (Cysteine Conjugate-Beta Lyase 2), is a pyridoxal phosphate-dependent aminotransferase involved in the kynurenine pathway of tryptophan degradation. This pathway produces neuroactive metabolites including kynurenic acid and quinolinic acid, which have opposing effects on [NMDA](/entities/nmda-receptor) receptor signaling. KYAT3 is implicated in epilepsy, Alzheimer's disease, and Parkinson's disease^[1].

Structure

KYAT3 contains key structural features:

• PLP-binding Domain: Pyridoxal phosphate cofactor for transamination
• Dimerization Interface: Forms functional homodimers
• Active Site Pocket: Substrate-specific binding for kynurenine and cysteine conjugates

Normal Function

KYAT3 participates in multiple metabolic pathways:

Kynurenine Pathway: Catalyzes transamination of kynurenine to kynurenic acid (KYNA)

Cysteine Metabolism: Acts as a cysteine S-conjugate beta-lyase

Neuroprotection: Produces KYNA, an endogenous NMDA receptor antagonist

Quinolinic Acid Regulation: Indirectly influences QA levels through pathway flux

Molecular Mechanism

KYAT3 functions through:

Transamination: Kynurenine + alpha-ketoglutarate → KYNA + glutamate

Cysteine Conjugate Beta-Lysis: Cleaves cysteine S-conjugates to produce pyruvate, ammonia, and thiols

PLP-dependent Catalysis: Uses vitamin B6 as a cofactor

Substrate Competition: Competes with KAT1/KAT2 for kynurenine

Role in Disease

Epilepsy

KYAT3 is critical in epilepsy pathophysiology:

• KYNA Deficiency: Reduced KYAT3 leads to lower KYNA, increasing excitotoxicity
• Seizure-Induced Changes: Acute seizures alter KYAT3 expression
• Therapeutic Target: KYNA-enhancing compounds are being explored^[2]

Alzheimer's Disease

KYAT3 plays complex roles in AD:

• KYNA/QA Balance: Shift toward quinolinic acid promotes neurodegeneration
• Microglial Activation: Alters neuroinflammatory responses
• Amyloid Effects: [Aβ](/proteins/amyloid-beta) may suppress KYAT3 expression

Parkinson's Disease

In PD, KYAT3 dysfunction contributes to:

• Dopaminergic Neuron Vulnerability: Altered kynurenine metabolism
• Neuroinflammation: Increased quinolinic acid toxicity
• Therapeutic Modulation: KYAT3 modulators being investigated

Therapeutic Approaches

Targeting KYAT3-related pathways:

KYNA Agonists: Enhance KYNA production for neuroprotection

Enzyme Modulators: Increase KYAT3 activity

Pathway Inhibitors: Block downstream quinolinic acid production

Dietary Interventions: Tryptophan modulation

Research Directions

Key areas of investigation:

• Understanding KYAT3 regulation in different brain cell types
• Developing selective KYAT3 modulators
• Biomarkers for kynurenine pathway activity
• Links between KYAT3 and other neurodegenerative processes

Background

The study of Kyat3 Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• KYAT3 Gene
• [Kynurenine Pathway](/mechanisms/kynurenine-pathway)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Epilepsy](/diseases/epilepsy)
• [Neuroinflammation Pathway](/mechanisms/neuroinflammation-pathway)

External Links

• [UniProt: KYAT3](https://www.uniprot.org/uniprot/Q9H3R9)
• [GeneCards: KYAT3](https://www.genecards.org/cgi-bin/carddisp.pl?gene=KYAT3)

Expression Pattern

KYAT3 (Kynurenine Aminotransferase 3), also known as CAT3, shows specific expression:

Brain Expression

• High expression: Cerebral cortex, hippocampus, basal ganglia
• Moderate expression: Cerebellum, thalamus, brainstem
• Cell type specificity: Primarily expressed in neurons, some astrocytic expression

Regulation

• Transcriptionally induced by inflammatory cytokines (IFN-γ, TNF-α)
• Epigenetic regulation via DNA methylation
• Activity modulated by vitamin B6 availability

Molecular Mechanisms

Catalytic Properties

KYAT3 catalyzes the transamination of kynurenine pathway intermediates:

• Primary substrate: 3-hydroxyanthranilic acid (3-HANA)
• Secondary substrates: Kynurenine, quinolinic acid
• Cofactor: Pyridoxal 5'-phosphate (PLP/vitamin B6)
• Product: 3-hydroxyanthranilic acid to quinolinic acid

Enzymatic Activity

• Irreversible step in kynurenine pathway
• Regulates flux toward NAD+ biosynthesis
• Controls levels of neuroactive metabolites

Brain-Specific Functions

In the brain, KYAT3:

• Modulates extracellular kynurenic acid levels
• Influences glutamatergic signaling via NMDA receptors
• Affects oxidative stress response

Disease Implications

Alzheimer's Disease

• Altered KYAT3 expression in AD brain
• Increased quinolinic acid neurotoxicity
• Potential therapeutic target for neuroprotection

Parkinson's Disease

• Dysregulated kynurenine pathway in PD
• KYAT3 as modulatory target
• Connection to mitochondrial dysfunction

Epilepsy

• Altered kynurenine metabolism in seizure disorders
• KYAT3 as anticonvulsant target

Therapeutic Approaches

| Approach | Strategy | Status |
|----------|----------|--------|
| KYAT3 inhibitors | Reduce toxic metabolites | Preclinical |
| Vitamin B6 supplementation | Enhance PLP availability | Clinical trials |
| Kynurenic acid analogs | Modulate NMDA signaling | Research |

Animal Models

Knockout Studies

• Kyat3-/- mice show altered kynurenine metabolism
• Increased susceptibility to neurotoxicity
• Behavioral phenotypes under investigation

Transgenic Models

• KYAT3 overexpression: Neuroprotective effects
• Useful for drug screening

Research Directions

[@schwarcz2012]

[@solvang]: Solvang WE, et al. CAT3/KYAT3 in bra[^7]: Potter MC, et al. Neurotoxic
[@erhardt2017]: Erhardt S, et al. Kynurenic acid and schizophrenia. Nat Rev Neurosci. 2017;18

References

[Guidetti P, et al, (2007) (2007)](https://pubmed.ncbi.nlm.nih.gov/17336322/)

[Potter MC, et al, (2010) (2010)](https://pubmed.ncbi.nlm.nih.gov/20133191/)

[Schwarcz R, et al, (2012) (2012)](https://pubmed.ncbi.nlm.nih.gov/22048464/)

[Haroutunian V, et al, (2015) (2015)](https://pubmed.ncbi.nlm.nih.gov/26250503/)

[Zádori D, et al, (2019) (2019)](https://pubmed.ncbi.nlm.nih.gov/31325492/)

Solvang WE, et al, CAT3/KYAT3 in bra[^7]: Potter MC, et al (n.d.)

Erhardt S, et al, Kynurenic acid and schizophrenia (2017)