• Carnitine is a quaternary ammonium compound.
  • In living cells, it is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids (fats) for the generation of metabolic energy
  • It is widely available as a nutritional supplement
  • Carnitine exists in two stereo isomers: Its biologically active form is L-carnitine, whereas its enantiomer, D-carnitine, is biologically inactive


  • In animals, the biosynthesis of carnitine occurs primarily in the liver and kidneys from the amino acids lysine (via trimethyllysine) and methionine
  • It is a method for the endogenous production of L-carnitine, a molecule that is essential for energy metabolism
  • Amino acid used in Carnitine synthesis is Lysine & Methionine

Utilization of carnitine?Carnitine transports long-chain acyl groupsfrom fatty acids into the mitochondrial matrix,so t...

  • Carnitine transports long-chain acyl groups from fatty acids into the mitochondrial matrix, so they can be broken down through β-oxidation to acetyl CoA to obtain usable energy via the citric acid cycle
  • Fatty acids must be activated before binding to the carnitine molecule to form ‘acylcarnitine’. 
  • The free fatty acid in the cytosol is attached with a thioester bond to coenzyme A (CoA). This reaction is catalyzed by the enzyme fatty acyl-CoAsynthetase
  • The acyl group on CoA can now be transferred to carnitine and the resulting acylcarnitine transported into the mitochondrial matrix. This occurs via a series of similar steps
  • Acyl CoA is transferred to the hydroxyl group of carnitine by carnitine acyltransferase I (palmitoyltransferase) located on the outer mitochondrial membrane
  • Acylcarnitine is shuttled inside by a carnitine-acylcarnitine translocase
  • Acylcarnitine is converted to acyl CoA by carnitine acyltransferase II (palmitoyltransferase) located on the inner mitochondrial membrane. The liberated carnitine returns to the cytosol.
  • Carnitine acyltransferase I undergoes allosteric inhibition as a result of malonyl-CoA, an intermediate in fatty acid biosynthesis, to prevent futile cycling between β-oxidation and fatty acid synthesis.
  • Carnitine palmitoyl transferase I is present in outer mitochondrial membrane & Carnitine palmitoyl trasferase II in inner  mitochondrial membrane


  • Heart conditions
  • Kidney disease and dialysis
  • Effect in male infertility
  • As a weight loss supplement:Carnitine is essential for transfer of fatty acids across mitochondrial membrane 
  • As an antidote in valproic acid poisoning
  • To improve symptoms in moderate asthmatics
  • To improve fatigue resulting from ifosfamide cancer chemotherapy
  • To treat symptoms of hyperthyroidism
Exam Question
  • Amino acid used in Carnitine synthesis is Lysine
  • The substance essential for transfer of fatty acids across mitochondrial membrane is Carnitine 
  • Carnitine is synthesised from Methionine
  • Carnitine  is involved in transport of long chain acyl-CoA in mitochondria
  • Hepatotoxicity caused by valproate can be prevented by Carnitine  
  • Carnitine palmitoyl transferase I is present in outer mitochondrial membrane & Carnitine palmitoyl trasferase II in inner  mitochondrial membrane
Don’t Forget to Solve all the previous Year Question asked on Carnitine

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