QPCT Protein
Introduction
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">QPCT Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td>QPCT</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Glutaminyl Cyclase</td>
</tr>
<tr>
<td class="label">Gene</td>
<td>QPCT</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q96KH6</td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td>2XUM, 3P40, 4E0L, 4E0M</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~38.5 kDa</td>
</tr>
<tr>
<td class="label">Length</td>
<td>360 amino acids</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Golgi apparatus, Secreted, Cytoplasm</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Metallo-dependent hydrolase family</td>
</tr>
<tr>
<td class="label">EC Number</td>
<td>3.5.5.1</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Company</td>
</tr>
<tr>
<td class="label">PQ912</td>
<td>Probiodrug</td>
</tr>
<tr>
<td class="label">PBD150</td>
<td>Probiodrug</td>
</tr>
<tr>
<td class="label">compound 5</td>
<td>Merck</td>
</tr>
<tr>
<td class="label">1,2,4-triazole derivatives</td>
<td>Various</td>
</tr>
<tr>
<td class="label">Biomarker</td>
<td>Source</td>
</tr>
<tr>
<td class="label">pE3-Aβ</td>
<td>CSF</td>
</tr>
<tr>
<td class="label">Total QPCT</td>
<td>Plasma</td>
</tr>
<tr>
<td class="lab
...QPCT Protein
Introduction
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">QPCT Protein</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td>QPCT</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Glutaminyl Cyclase</td>
</tr>
<tr>
<td class="label">Gene</td>
<td>QPCT</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q96KH6</td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td>2XUM, 3P40, 4E0L, 4E0M</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~38.5 kDa</td>
</tr>
<tr>
<td class="label">Length</td>
<td>360 amino acids</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Golgi apparatus, Secreted, Cytoplasm</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Metallo-dependent hydrolase family</td>
</tr>
<tr>
<td class="label">EC Number</td>
<td>3.5.5.1</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Company</td>
</tr>
<tr>
<td class="label">PQ912</td>
<td>Probiodrug</td>
</tr>
<tr>
<td class="label">PBD150</td>
<td>Probiodrug</td>
</tr>
<tr>
<td class="label">compound 5</td>
<td>Merck</td>
</tr>
<tr>
<td class="label">1,2,4-triazole derivatives</td>
<td>Various</td>
</tr>
<tr>
<td class="label">Biomarker</td>
<td>Source</td>
</tr>
<tr>
<td class="label">pE3-Aβ</td>
<td>CSF</td>
</tr>
<tr>
<td class="label">Total QPCT</td>
<td>Plasma</td>
</tr>
<tr>
<td class="label">QPCT activity</td>
<td>Plasma</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Qpct 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.
Overview
Glutaminyl Cyclase (QPCT) is a 360-amino acid enzyme that catalyzes the conversion of N-terminal glutamine residues to pyroglutamate (pGlu) residues. This post-translational modification, known as pyroglutamylation, has profound implications for protein stability, aggregation propensity, and biological activity. QPCT has emerged as a significant therapeutic target in Alzheimer's disease (AD) due to its critical role in generating highly neurotoxic pyroglutamate-modified [amyloid-beta](/proteins/amyloid-beta) (pE3-Aβ) species. [@pyroglutamatemodified2013]
Structure
Domain Architecture
The QPCT protein consists of a single catalytic domain with a characteristic α/β/α sandwich fold. The active site contains a zinc ion (Zn²⁺) that is essential for catalytic activity [1]. Key structural features include:
N-terminal Domain: Contains the active site with zinc-binding motif
Central β-sheet: Core structural element surrounded by α-helices
C-terminal Region: Involved in substrate recognition and dimerizationActive Site
The active site of QPCT features a zinc ion coordinated by:
- Histidine residues (His319, His321, His340)
- Aspartate (Asp248)
- A water molecule
This zinc-dependent mechanism allows for efficient catalysis of glutamine cyclization [1].
Molecular Function
Catalytic Activity
QPCT catalyzes the intramolecular cyclization of N-terminal glutamine residues to form pyroglutamate (pGlu) residues. The reaction proceeds through the following mechanism:
N-terminal Gln → (QPCT) → Pyroglutamate (pGlu) + NH₃
The enzyme exhibits:
- High specificity for N-terminal glutamine
- Optimal pH of 7.0-8.0
- Zinc-dependent catalysis
- KM ~ 10-50 μM for various substrates
Biological Pathways
QPCT participates in several important biological pathways:
Protein Quality Control: Modifies proteins to alter their degradation fate
Amyloid Processing: Generates pE3-Aβ in Alzheimer's disease
Peptide Hormone Maturation: Processes various bioactive peptides
ER-Golgi Processing: Involved in post-translational modificationRole in Disease
Alzheimer's Disease
QPCT plays a central role in AD pathogenesis through the generation of pE3-Aβ [2][3]:
- Toxicity: pE3-Aβ is 10-100x more toxic than unmodified Aβ
- Seeding: Acts as a nucleus for plaque formation
- Resistance: More resistant to clearance mechanisms
- Spread: Facilitates propagation of pathology
Key Mechanisms:
QPCT expression is upregulated in AD brain [4]
pE3-Aβ triggers neuroinflammation
Promotes synaptic dysfunction
Accelerates [tau](/proteins/tau) pathologyAmyotrophic Lateral Sclerosis
In ALS, QPCT may contribute to:
- [TDP-43](/proteins/tdp-43) protein aggregation
- Motor neuron degeneration
- Protein homeostasis disruption
Prion Disease
QPCT activity may influence prion protein aggregation and conversion to the pathogenic prion form.
Therapeutic Targeting
QPCT Inhibitors
Multiple pharmaceutical companies have developed QPCT inhibitors:
Clinical Development
PQ912 (Wagabate):
- First oral QPCT inhibitor in clinical trials
- Showed target engagement and reduction of pE3-Aβ in CSF
- Improved synaptic function in Phase 1 trials
- Phase 2a study in early AD patients [5]
Therapeutic Strategies
Inhibitor Development: Small molecule inhibitors
Immunotherapy: Antibodies against pE3-Aβ
Gene Therapy: siRNA approaches to reduce QPCT expression
Combination Therapy: QPCT inhibitors with BACE inhibitorsExpression and Regulation
Tissue Distribution
QPCT is expressed in:
- Brain: [Cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), basal ganglia
- Liver: Hepatocytes
- Kidney: Renal tubules
- Endocrine Tissues: Pituitary, adrenal
Cellular Localization
- Golgi apparatus: Primary localization
- Secretory vesicles: For extracellular release
- Cytoplasm: Lower expression
- Extracellular space: Secreted form
Transcriptional Regulation
QPCT expression is regulated by:
- Inflammatory cytokines (IL-1β, TNF-α)
- Aβ itself (positive feedback)
- Cellular stress conditions
Research Directions
Biomarker Development
- pE3-Aβ in CSF as a biomarker
- QPCT activity measurement in plasma
- Genetic variants affecting QPCT expression
Biomarker Table
Future Research
- Structural studies of QPCT-inhibitor complexes
- Development of brain-penetrant inhibitors
- Understanding QPCT's physiological substrates
- Biomarker validation in large cohorts
Summary
QPCT (Glutaminyl Cyclase) is a zinc-dependent enzyme that catalyzes the formation of pyroglutamate-modified proteins. Its critical role in generating toxic pE3-Aβ species makes it a compelling therapeutic target in Alzheimer's disease. QPCT inhibitors, particularly PQ912, have advanced to clinical trials and represent a promising disease-modifying approach for AD and potentially other neurodegenerative conditions characterized by protein aggregation.
Background
The study of Qpct 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.
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
- [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
- [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data
See Also
- [QPCT Gene](/genes/qpct)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Amyloid Cascade Hypothesis](/mechanisms/amyloid-cascade)
- [Protein Quality Control](/mechanisms/protein-quality-control-network)
- [Pyroglutamate Modification](/entities/glutamate)
- [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
- QPCT Inhibitors
- [Protein Aggregation](/mechanisms/protein-aggregation)
- [QPCT UniProt](https://www.uniprot.org/uniprotkb/Q96KH6/entry)
- [PDB 2XUM](https://www.ebi.ac.uk/pdbe/entry/pdb/2xum/)
- [ClinicalTrials.gov QPCT](https://clinicaltrials.gov/search?term=glutaminyl+cyclase)