CYP3A4 — Cytochrome P450 3A4 is the most important cytochrome P450 enzyme in drug metabolism, responsible for metabolizing approximately 50% of all drugs used clinically. This page provides detailed information about its structure, function, and relevance to neurodegenerative diseases.
| Cytochrome P450 3A4 | |
|---|---|
| Gene Symbol | CYP3A4 |
| Full Name | Cytochrome P450 Family 3 Subfamily A Member 4 |
| Chromosome | 7q21.1 |
| NCBI Gene ID | [1579](https://www.ncbi.nlm.nih.gov/gene/1579) |
| OMIM | 171696 |
| Ensembl ID | ENSG00000123338 |
| UniProt ID | [P08684](https://www.uniprot.org/uniprot/P08684) |
| Associated Diseases | Parkinson's Disease, Drug Metabolism Disorders, Drug-Drug Interactions |
CYP3A4 is the dominant Phase I drug-metabolizing enzyme in humans, expressed primarily in the liver and intestinal mucosa. It catalyzes the oxidation, reduction, and hydrolysis of a vast array of pharmaceutical agents, steroids, and xenobiotics. Unlike CYP2D6, which is not inducible, CYP3A4 activity can be significantly increased by exposure to certain drugs (induction) or decreased by inhibitors.
CYP3A4 encodes cytochrome P450 3A4, which plays a critical role in:
| Drug Class | Examples | Relevance to CBS/PSP |
|---|---|---|
| Benzodiazepines | Clonazepam, Alprazolam, Diazepam | Anxiety, sleep, myoclonus |
| Calcium Channel Blockers | Amlodipine, Nifedipine | BP management |
| Statins | Atorvastatin, Simvastatin | Cardiovascular protection |
| Dopamine Agonists | Bromocriptine, Cabergoline | Motor symptoms |
| Immunosuppressants | N/A | Not commonly used |
CYP3A4 polymorphisms are less common than in CYP2D6 but can significantly affect drug metabolism:
| Allele | Function | Frequency | Clinical Implication |
|---|---|---|---|
| *1 (wild-type) | Normal | Most common | Standard metabolism |
| *22 | Reduced | 2-4% (European) | Reduced substrate clearance |
| *1B | Normal | Variable | Generally normal function |
For Levodopa:
For Rasagiline:
For Clonazepam:
For Dopamine Agonists:
| Disease | Variants | Inheritance | Mechanism |
|---|---|---|---|
| Parkinson's Disease | Various | Risk factor (indirect) | Drug metabolism alterations |
| Drug Metabolism Disorders | Various | Various | Poor/ultra-rapid metabolizer status |
Inhibitors: Avoid strong CYP3A4 inhibitors when possible, or reduce doses
Inducers: May reduce efficacy of CYP3A4 substrates
Grapefruit Juice: Inhibits CYP3A4 — advise patients to avoid