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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed July 2010

What is the official name of the PMM2 gene?

The official name of this gene is “phosphomannomutase 2.”

PMM2 is the gene's official symbol. The PMM2 gene is also known by other names, listed below.

What is the normal function of the PMM2 gene?

The PMM2 gene provides instructions for making an enzyme called phosphomannomutase 2 (PMM2). This enzyme is involved in a process called glycosylation, which attaches groups of sugar molecules (oligosaccharides) to proteins. Oligosaccharides are made up of many small sugar molecules that are attached to one another in a long chain. Glycosylation modifies proteins so they can perform a wider variety of functions. In one of the early steps of glycosylation, the PMM2 enzyme converts a molecule called mannose-6-phosphate to mannose-1-phosphate. Subsequently, mannose-1-phosphate is converted into GDP-mannose, which can transfer its small sugar molecule called mannose to the growing oligosaccharide chain. Once the correct number of small sugar molecules are linked together to form the oligosaccharide, it can be attached to a protein.

How are changes in the PMM2 gene related to health conditions?

PMM2-congenital disorder of glycosylation - caused by mutations in the PMM2 gene

More than 115 mutations in the PMM2 gene have been found to cause PMM2-congenital disorder of glycosylation (PMM2-CDG, also known as congenital disorder of glycosylation type Ia). This is a severe condition that is characterized by developmental delay, weak muscle tone (hypotonia), abnormal distribution of fat, and various other signs and symptoms. The mutations that cause PMM2-CDG change the structure of the PMM2 enzyme in different ways; however, all of the mutations appear to result in reduced enzyme activity. Decreased activity of the PMM2 enzyme leads to a shortage of GDP-mannose within cells. As a result, there is not enough activated mannose to form oligosaccharides. Glycosylation cannot proceed normally because incorrect oligosaccharides are produced. The signs and symptoms in PMM2-CDG are likely due to the production of abnormally glycosylated proteins in many organs and tissues.

Where is the PMM2 gene located?

Cytogenetic Location: 16p13

Molecular Location on chromosome 16: base pairs 8,797,813 to 8,855,197

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The PMM2 gene is located on the short (p) arm of chromosome 16 at position 13.

The PMM2 gene is located on the short (p) arm of chromosome 16 at position 13.

More precisely, the PMM2 gene is located from base pair 8,797,813 to base pair 8,855,197 on chromosome 16.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about PMM2?

You and your healthcare professional may find the following resources about PMM2 helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the PMM2 gene or gene products?

  • CDG1a
  • phosphomannomutase
  • PMM

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding PMM2?

congenital ; developmental delay ; enzyme ; gene ; glycosylation ; hypotonia ; mannose ; molecule ; muscle tone ; oligosaccharides ; phosphate ; protein

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • de la Morena-Barrio ME, Hernández-Caselles T, Corral J, García-López R, Martínez-Martínez I, Pérez-Dueñas B, Altisent C, Sevivas T, Kristensen SR, Guillén-Navarro E, Miñano A, Vicente V, Jaeken J, Lozano ML. GPI-anchor and GPI-anchored protein expression in PMM2-CDG patients. Orphanet J Rare Dis. 2013 Oct 20;8:170. doi: 10.1186/1750-1172-8-170. (
  • Freeze HH. Towards a therapy for phosphomannomutase 2 deficiency, the defect in CDG-Ia patients. Biochim Biophys Acta. 2009 Sep;1792(9):835-40. doi: 10.1016/j.bbadis.2009.01.004. Review. (
  • Gao N, Shang J, Lehrman MA. Analysis of glycosylation in CDG-Ia fibroblasts by fluorophore-assisted carbohydrate electrophoresis: implications for extracellular glucose and intracellular mannose 6-phosphate. J Biol Chem. 2005 May 6;280(18):17901-9. Epub 2005 Feb 11. (
  • Gene Review: PMM2-CDG (CDG-Ia) (
  • Grünewald S. The clinical spectrum of phosphomannomutase 2 deficiency (CDG-Ia). Biochim Biophys Acta. 2009 Sep;1792(9):827-34. doi: 10.1016/j.bbadis.2009.01.003. Epub 2009 Jan 14. Review. (
  • Haeuptle MA, Hennet T. Congenital disorders of glycosylation: an update on defects affecting the biosynthesis of dolichol-linked oligosaccharides. Hum Mutat. 2009 Dec;30(12):1628-41. doi: 10.1002/humu.21126. Review. (
  • NCBI Gene (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: July 2010
Published: February 8, 2016