QPCT Protein

📖 Wiki Page

protein953 wordssynced 2026-04-02

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

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]

Protein Information

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 dimerization

Active 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 modification

Role 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) pathology

Amyotrophic 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 inhibitors

Expression 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

QPCT Protein

QPCT Protein

Introduction

QPCT Protein

Introduction

Overview

Protein Information

Structure

Domain Architecture

Active Site

Molecular Function

Catalytic Activity

Biological Pathways

Role in Disease

Alzheimer's Disease

Amyotrophic Lateral Sclerosis

Prion Disease

Therapeutic Targeting

QPCT Inhibitors

Clinical Development

Therapeutic Strategies

Expression and Regulation

Tissue Distribution

Cellular Localization

Transcriptional Regulation

Research Directions

Biomarker Development

Biomarker Table

Future Research

Summary

Background

External Links

See Also