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CPT2 gene
URL of this page: https://medlineplus.gov/genetics/gene/cpt2/

CPT2 gene

carnitine palmitoyltransferase 2

Normal Function

The CPT2 gene provides instructions for making an enzyme called carnitine palmitoyltransferase 2. This enzyme is essential for fatty acid oxidation, a multistep process that breaks down (metabolizes) fats and converts them into energy. Fatty acids are a major source of energy for the heart and muscles. During periods of fasting, fatty acids are also an important energy source for the liver and other tissues.

Within liver cells, fatty acid oxidation takes place within mitochondria, which are the energy-producing centers in cells.  Before they can enter mitochondria, a group of fats called long-chain fatty acids must first attach to a compound called carnitine. Once inside mitochondria, carnitine palmitoyltransferase 2 removes the carnitine from these fatty acids and adds a substance called coenzyme A. Long-chain fatty acids must be joined to coenzyme A before they can be metabolized to produce energy. 

Health Conditions Related to Genetic Changes

Carnitine palmitoyltransferase II deficiency

Variants (also called mutations) in the CPT2 have been found to cause carnitine palmitoyltransferase II (CPT II) deficiency. CPT II deficiency is a condition that prevents the body from using certain fats for energy. This condition can cause serious health problems, particularly during periods of fasting. 

The CPT2 gene variants that cause CPT II deficiency lead to the production of carnitine palmitoyltransferase 2 enzymes with reduced levels of activity. Variants that severely reduce enzyme activity typically cause the more severe forms of CPT II deficiency (the lethal neonatal form and the severe infantile hepatocardiomuscular form), while those that partially reduce enzyme activity usually cause the less severe myopathic form of the disorder. The most common CPT2 gene variant replaces the protein building block (amino acid) serine with the amino acid leucine at position 113 (written as Ser113Leu or S113L) in the enzyme. This variant accounts for about 60 percent of the variants that cause the myopathic form of CPT II deficiency.

Without enough functioning carnitine palmitoyltransferase 2, long-chain fatty acids are not properly processed after they enter mitochondria. As a result, these fats cannot be broken down to produce energy. This can lead to some of the features of CPT II deficiency, such as muscle pain, muscle weakness, and low levels of glucose in the blood (hypoglycemia). Normally, the breakdown of fats also produces molecules called ketones, which can be used for energy. If the process of breaking down fats is interrupted due to low levels of carnitine palmitoyltransferase 2, it can also cause low levels of ketones (hypoketosis). Fatty acids that are still attached to carnitine (known as long-chain acylcarnitines) may build up in cells and damage the liver, heart, and muscles. This abnormal buildup causes the other signs and symptoms of CPT II deficiency.

More About This Health Condition

Other Names for This Gene

  • CPT II
  • CPT2_HUMAN
  • CPTASE

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Corti S, Bordoni A, Ronchi D, Musumeci O, Aguennouz M, Toscano A, Lamperti C, Bresolin N, Comi GP. Clinical features and new molecular findings in Carnitine Palmitoyltransferase II (CPT II) deficiency. J Neurol Sci. 2008 Mar 15;266(1-2):97-103. doi: 10.1016/j.jns.2007.09.015. Epub 2007 Oct 23. Citation on PubMed
  • Deschauer M, Wieser T, Zierz S. Muscle carnitine palmitoyltransferase II deficiency: clinical and molecular genetic features and diagnostic aspects. Arch Neurol. 2005 Jan;62(1):37-41. doi: 10.1001/archneur.62.1.37. Citation on PubMed
  • Illsinger S, Lucke T, Peter M, Ruiter JP, Wanders RJ, Deschauer M, Handig I, Wuyts W, Das AM. Carnitine-palmitoyltransferase 2 deficiency: novel mutations and relevance of newborn screening. Am J Med Genet A. 2008 Nov 15;146A(22):2925-8. doi: 10.1002/ajmg.a.32545. Citation on PubMed
  • Isackson PJ, Bennett MJ, Lichter-Konecki U, Willis M, Nyhan WL, Sutton VR, Tein I, Vladutiu GD. CPT2 gene mutations resulting in lethal neonatal or severe infantile carnitine palmitoyltransferase II deficiency. Mol Genet Metab. 2008 Aug;94(4):422-427. doi: 10.1016/j.ymgme.2008.05.002. Epub 2008 Jun 11. Citation on PubMed
  • Joshi PR, Zierz S. Muscle Carnitine Palmitoyltransferase II (CPT II) Deficiency: A Conceptual Approach. Molecules. 2020 Apr 13;25(8):1784. doi: 10.3390/molecules25081784. Citation on PubMed
  • Longo N, Amat di San Filippo C, Pasquali M. Disorders of carnitine transport and the carnitine cycle. Am J Med Genet C Semin Med Genet. 2006 May 15;142C(2):77-85. doi: 10.1002/ajmg.c.30087. Citation on PubMed or Free article on PubMed Central
  • Olpin SE, Afifi A, Clark S, Manning NJ, Bonham JR, Dalton A, Leonard JV, Land JM, Andresen BS, Morris AA, Muntoni F, Turnbull D, Pourfarzam M, Rahman S, Pollitt RJ. Mutation and biochemical analysis in carnitine palmitoyltransferase type II (CPT II) deficiency. J Inherit Metab Dis. 2003;26(6):543-57. doi: 10.1023/a:1025947930752. Citation on PubMed
  • Orngreen MC, Duno M, Ejstrup R, Christensen E, Schwartz M, Sacchetti M, Vissing J. Fuel utilization in subjects with carnitine palmitoyltransferase 2 gene mutations. Ann Neurol. 2005 Jan;57(1):60-6. doi: 10.1002/ana.20320. Citation on PubMed
  • Ramsay RR, Zammit VA. Carnitine acyltransferases and their influence on CoA pools in health and disease. Mol Aspects Med. 2004 Oct-Dec;25(5-6):475-93. doi: 10.1016/j.mam.2004.06.002. Citation on PubMed
  • Sigauke E, Rakheja D, Kitson K, Bennett MJ. Carnitine palmitoyltransferase II deficiency: a clinical, biochemical, and molecular review. Lab Invest. 2003 Nov;83(11):1543-54. doi: 10.1097/01.lab.0000098428.51765.83. Citation on PubMed
  • Wieser T. Carnitine Palmitoyltransferase II Deficiency. 2004 Aug 27 [updated 2019 Jan 3]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from http://www.ncbi.nlm.nih.gov/books/NBK1253/ Citation on PubMed

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