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ST3GAL5 gene

ST3 beta-galactoside alpha-2,3-sialyltransferase 5

Normal Function

The ST3GAL5 gene provides instructions for making an enzyme called GM3 synthase. This enzyme carries out a chemical reaction that is the first step in the production of certain fatty molecules (lipids) called gangliosides. Specifically, GM3 synthase converts a molecule called lactosylceramide to a simple ganglioside called GM3. Further reactions use GM3 to create more complex gangliosides.

Gangliosides are present on the surface of cells and tissues throughout the body, and they are particularly abundant in the nervous system. Although their exact functions are unclear, studies suggest that these molecules help regulate chemical signaling pathways that influence cell growth and division (proliferation), cell movement (motility), the attachment of cells to one another (adhesion), and cell survival. Gangliosides appear to be important for normal brain development and function.

Health Conditions Related to Genetic Changes

GM3 synthase deficiency

At least one mutation in the ST3GAL5 gene has been found to cause GM3 synthase deficiency, a condition characterized by recurrent seizures (epilepsy) and problems with brain development. The known mutation replaces a single protein building block (amino acid), arginine, with a signal to stop protein production prematurely. The mutation is written as Arg288Ter or R288X, although in older scientific articles it is sometimes written as Arg232Ter or R232X. The mutation prevents the production of any functional GM3 synthase. Without this enzyme, cells cannot produce GM3 or other gangliosides normally. It is unclear how a loss of this enzyme leads to the signs and symptoms of GM3 synthase deficiency. Researchers are working to determine whether it is the lack of gangliosides or a buildup of compounds used to make gangliosides, or both, that underlies the seizures and other problems with brain development that occur in this condition.

More About This Health Condition

Other Names for This Gene

  • alpha 2,3-sialyltransferase V
  • CMP-NeuAc:lactosylceramide alpha-2,3-sialyltransferase
  • ganglioside GM3 synthase
  • GM3 synthase
  • lactosylceramide alpha-2,3-sialyltransferase
  • lactosylceramide alpha-2,3-sialyltransferase isoform 1
  • lactosylceramide alpha-2,3-sialyltransferase isoform 2
  • SATI
  • sialyltransferase 9 (CMP-NeuAc:lactosylceramide alpha-2,3-sialyltransferase; GM3 synthase)
  • SIAT9
  • ST3Gal V
  • ST3GalV

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


  • Fragaki K, Ait-El-Mkadem S, Chaussenot A, Gire C, Mengual R, Bonesso L, Beneteau M, Ricci JE, Desquiret-Dumas V, Procaccio V, Rotig A, Paquis-Flucklinger V. Refractory epilepsy and mitochondrial dysfunction due to GM3 synthase deficiency. Eur J Hum Genet. 2013 May;21(5):528-34. doi: 10.1038/ejhg.2012.202. Epub 2012 Sep 19. Citation on PubMed or Free article on PubMed Central
  • Ishii A, Ohta M, Watanabe Y, Matsuda K, Ishiyama K, Sakoe K, Nakamura M, Inokuchi J, Sanai Y, Saito M. Expression cloning and functional characterization of human cDNA for ganglioside GM3 synthase. J Biol Chem. 1998 Nov 27;273(48):31652-5. doi: 10.1074/jbc.273.48.31652. Citation on PubMed
  • Kim KW, Kim SW, Min KS, Kim CH, Lee YC. Genomic structure of human GM3 synthase gene (hST3Gal V) and identification of mRNA isoforms in the 5'-untranslated region. Gene. 2001 Aug 8;273(2):163-71. doi: 10.1016/s0378-1119(01)00595-9. Citation on PubMed
  • Liu Y, Su Y, Wiznitzer M, Epifano O, Ladisch S. Ganglioside depletion and EGF responses of human GM3 synthase-deficient fibroblasts. Glycobiology. 2008 Aug;18(8):593-601. doi: 10.1093/glycob/cwn039. Epub 2008 May 14. Citation on PubMed
  • Prokazova NV, Samovilova NN, Gracheva EV, Golovanova NK. Ganglioside GM3 and its biological functions. Biochemistry (Mosc). 2009 Mar;74(3):235-49. doi: 10.1134/s0006297909030018. Citation on PubMed
  • Simpson MA, Cross H, Proukakis C, Priestman DA, Neville DC, Reinkensmeier G, Wang H, Wiznitzer M, Gurtz K, Verganelaki A, Pryde A, Patton MA, Dwek RA, Butters TD, Platt FM, Crosby AH. Infantile-onset symptomatic epilepsy syndrome caused by a homozygous loss-of-function mutation of GM3 synthase. Nat Genet. 2004 Nov;36(11):1225-9. doi: 10.1038/ng1460. Epub 2004 Oct 24. 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.