Biochemistry · Molecule
Carnitine (L-carnitine) !
Carnitine is the carrier that takes long-chain fatty acids into the mitochondrion to be burned.
Updated 2026-11-01
Loading the 3D model…
Key facts
- Comes from meat and dairy and is made in liver and kidney from lysine and methionine (needs vitamin C).
- Enters cells through the OCTN2 transporter (SLC22A5 gene); the kidney reabsorbs it through the same transporter.
- Carries the acyl group as acylcarnitine across the inner membrane (CPT-I, CACT, CPT-II).
- Blood acylcarnitines are the basis of newborn screening for β-oxidation defects.
- Also called
- Levocarnitine, β-Hydroxy-γ-trimethylaminobutyrate
- Formula
- C₇H₁₅NO₃
- PubChem
- CID 10917
Structure
- A small molecule with a quaternary ammonium and a hydroxyl group that forms the ester with the fatty acid.
Clinical notes
- Primary deficiency (OCTN2): very low carnitine, hypoketotic hypoglycaemia and cardiomyopathy; responds to oral carnitine.
- Secondary deficiency: dialysis, valproic acid, organic acidurias (lost as acylcarnitine) and some formulas.
Pathways
Related conditions
- Primary carnitine deficiency
- Carnitine palmitoyltransferase II (CPT-II) deficiency
- Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency
Related
- Carnitine shuttle
- Carnitine palmitoyltransferase I (CPT-I)
- Palmitate (palmitic acid)
- Medium-chain acyl-CoA dehydrogenase (MCAD)
Test yourself
Think of the answer, then tap the question to see it.
Which transporter carries carnitine into cells?
OCTN2, encoded by SLC22A5; it also reabsorbs carnitine in the kidney.
From which amino acids is carnitine made?
From lysine and methionine, with the help of vitamin C.
Why can valproic acid lower carnitine?
It forms valproylcarnitine, which is lost in urine and drags free carnitine with it.
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: (-)-Carnitine (CID 10917) (PubChem, NCBI, 2026) · Public domain; Carnitine shuttle (Reactome, 2026); SLC22A5 gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.