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CYP27A1 gene

cytochrome P450 family 27 subfamily A member 1

Normal Function

The CYP27A1 gene is a member of the cytochrome P450 gene family. Enzymes produced from the cytochrome P450 genes are involved in the formation and breakdown of various molecules and chemicals within cells. The CYP27A1 gene provides instructions for producing an enzyme called sterol 27-hydroxylase. This enzyme is located in the energy-producing centers of cells (mitochondria), where it is involved in the pathway that breaks down cholesterol to form acids used to digest fats (bile acids). Specifically, sterol 27-hydroxylase breaks down cholesterol to form a bile acid called chenodeoxycholic acid. The formation of bile acids from cholesterol is the body's main pathway for cholesterol removal. Sterol 27-hydroxylase plays a key role in maintaining normal cholesterol levels in the body.

Health Conditions Related to Genetic Changes

Cerebrotendinous xanthomatosis

At least 90 mutations that cause cerebrotendinous xanthomatosis have been identified in the CYP27A1 gene. Cerebrotendinous xanthomatosis is a disorder characterized by abnormal storage of fats (lipids) in many areas of the body. Most CYP27A1 gene mutations change one protein building block (amino acid) in the sterol 27-hydroxylase enzyme. The most common mutation changes the amino acid arginine to the amino acid cysteine at position 362 in the protein (written as Arg362Cys or R362C). Changes in amino acids typically disrupt the normal function of the protein and impair its ability to help form chenodeoxycholic acid. Other mutations cause no functional enzyme to be made. As a result, other molecules are formed by an alternative pathway. A molecule called cholestanol, which is similar to cholesterol, is produced and accumulates in blood and tissues. Cholesterol also accumulates in tissues, but levels in blood are typically normal. The accumulation of cholesterol and cholestanol throughout the body's tissues causes the signs and symptoms of cerebrotendinous xanthomatosis.

More About This Health Condition

Other Names for This Gene

  • 5-beta-cholestane-3-alpha, 7-alpha, 12-alpha-triol 27-hydroxylase
  • CP27
  • CTX
  • CYP27
  • cytochrome P-450C27/25
  • cytochrome P450, family 27, subfamily A, polypeptide 1
  • cytochrome P450, subfamily XXVIIA (steroid 27-hydroxylase, cerebrotendinous xanthomatosis), polypeptide 1
  • sterol 27-hydroxylase
  • vitamin D(3) 25-hydroxylase

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


  • Araya Z, Tang W, Wikvall K. Hormonal regulation of the human sterol 27-hydroxylase gene CYP27A1. Biochem J. 2003 Jun 1;372(Pt 2):529-34. doi: 10.1042/BJ20021651. Citation on PubMed or Free article on PubMed Central
  • Bjorkhem I, Hansson M. Cerebrotendinous xanthomatosis: an inborn error in bile acid synthesis with defined mutations but still a challenge. Biochem Biophys Res Commun. 2010 May 21;396(1):46-9. doi: 10.1016/j.bbrc.2010.02.140. Citation on PubMed
  • Bjorkhem I. Cerebrotendinous xanthomatosis. Curr Opin Lipidol. 2013 Aug;24(4):283-7. doi: 10.1097/MOL.0b013e328362df13. Citation on PubMed
  • Gallus GN, Dotti MT, Federico A. Clinical and molecular diagnosis of cerebrotendinous xanthomatosis with a review of the mutations in the CYP27A1 gene. Neurol Sci. 2006 Jun;27(2):143-9. doi: 10.1007/s10072-006-0618-7. Citation on PubMed
  • Nie S, Chen G, Cao X, Zhang Y. Cerebrotendinous xanthomatosis: a comprehensive review of pathogenesis, clinical manifestations, diagnosis, and management. Orphanet J Rare Dis. 2014 Nov 26;9:179. doi: 10.1186/s13023-014-0179-4. Citation on PubMed or Free article on PubMed Central
  • Norlin M, von Bahr S, Bjorkhem I, Wikvall K. On the substrate specificity of human CYP27A1: implications for bile acid and cholestanol formation. J Lipid Res. 2003 Aug;44(8):1515-22. doi: 10.1194/jlr.M300047-JLR200. Epub 2003 Jun 1. Citation on PubMed
  • von Bahr S, Movin T, Papadogiannakis N, Pikuleva I, Ronnow P, Diczfalusy U, Bjorkhem I. Mechanism of accumulation of cholesterol and cholestanol in tendons and the role of sterol 27-hydroxylase (CYP27A1). Arterioscler Thromb Vasc Biol. 2002 Jul 1;22(7):1129-35. doi: 10.1161/01.atv.0000022600.61391.a5. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.