Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions About   Site Map   Contact Us
Home A service of the U.S. National Library of Medicine®
Printer-friendly version


Reviewed August 2012

What is the official name of the CYBB gene?

The official name of this gene is “cytochrome b-245, beta polypeptide.”

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

Read more about gene names and symbols on the About page.

What is the normal function of the CYBB gene?

The CYBB gene provides instructions for making a protein called cytochrome b-245, beta subunit (also known as p91-phox). This protein is one part (subunit) of a group of proteins that forms an enzyme complex called NADPH oxidase, which plays an essential role in the immune system. Within this complex, the cytochrome b-245, beta subunit has an alpha subunit partner (produced from the CYBA gene). Both alpha and beta subunits are required for either to function and the NADPH oxidase complex requires both subunits in order to be functional. NADPH oxidase is primarily active in immune system cells called phagocytes. These cells catch and destroy foreign invaders such as bacteria and fungi. NADPH oxidase is also thought to regulate the activity of immune cells called neutrophils. These cells play a role in adjusting the inflammatory response to optimize healing and reduce injury to the body.

The presence of foreign invaders stimulates phagocytes and triggers the assembly of NADPH oxidase. This enzyme participates in a chemical reaction that converts oxygen to a toxic molecule called superoxide. Superoxide is used to generate several other compounds, including hydrogen peroxide (a strong disinfectant) and hypochlorous acid (the active ingredient in bleach). These highly reactive, toxic substances are known as reactive oxygen species. Phagocytes use these substances to kill foreign invaders, preventing them from reproducing in the body and causing illness.

Does the CYBB gene share characteristics with other genes?

The CYBB gene belongs to a family of genes called CYB (cytochrome b).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? in the Handbook.

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

chronic granulomatous disease - caused by mutations in the CYBB gene

More than 650 mutations in the CYBB gene have been found to cause chronic granulomatous disease. People with this disorder are at increased risk of developing recurrent episodes of infection and inflammation due to a weakened immune system. Mutations in the CYBB gene cause approximately 70 percent of all cases of this condition. Most of these mutations change single building blocks of protein (amino acids) in the cytochrome b-245, beta subunit or cause it to be abnormally short and nonfunctional. An altered protein not only diminishes the function of the beta subunit, but the function of its alpha subunit partner as well. Without these subunits, NADPH oxidase cannot assemble or function properly. As a result, phagocytes are unable to produce reactive oxygen species to kill foreign invaders, and neutrophil activity is not regulated. A lack of NADPH oxidase leaves affected individuals vulnerable to many types of infection and excessive inflammation.

Where is the CYBB gene located?

Cytogenetic Location: Xp21.1

Molecular Location on the X chromosome: base pairs 37,780,017 to 37,813,465

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBIThis link leads to a site outside Genetics Home Reference.)

The CYBB gene is located on the short (p) arm of the X chromosome at position 21.1.

The CYBB gene is located on the short (p) arm of the X chromosome at position 21.1.

More precisely, the CYBB gene is located from base pair 37,780,017 to base pair 37,813,465 on the X chromosome.

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

Where can I find additional information about CYBB?

You and your healthcare professional may find the following resources about CYBB 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 CYBB gene or gene products?

  • CGD91-phox
  • cytochrome b-245 heavy chain
  • cytochrome b558 subunit beta
  • cytochrome b(558) subunit beta
  • GP91-1
  • GP91PHOX
  • neutrophil cytochrome b 91 kDa polypeptide
  • p91-PHOX
  • superoxide-generating NADPH oxidase heavy chain subunit

Where can I find general information about genes?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding CYBB?

acids ; bacteria ; chronic ; enzyme ; gene ; granulomatous ; hydrogen peroxide ; hypochlorous acid ; immune system ; infection ; inflammation ; injury ; molecule ; neutrophils ; oxidase ; oxygen ; phagocytes ; protein ; reactive oxygen species ; subunit ; toxic

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

See also Understanding Medical Terminology.

References (6 links)


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: August 2012
Published: February 8, 2016