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Reviewed December 2014
What is the official name of the BTD gene?
The official name of this gene is “biotinidase.”
BTD is the gene's official symbol. The BTD 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 BTD gene?
The BTD gene provides instructions for making an enzyme called biotinidase. This enzyme recycles biotin, a B vitamin found in foods such as liver, egg yolks, and milk. Biotinidase removes biotin that is bound to proteins in food, leaving the vitamin in its free (unbound) state. The body needs free biotin to activate enzymes called biotin-dependent carboxylases. These carboxylases are involved in many critical cellular functions, including the breakdown of proteins, fats, and carbohydrates.
In addition to processing biotin obtained from the diet, biotinidase recycles biotin within the body. As biotin-dependent carboxylases are broken down, they release a molecule called biocytin. Biocytin is a complex made of up biotin and a protein building block (amino acid) called lysine. Biotinidase splits this complex, making free biotin available for reuse by other carboxylase enzymes.
Researchers suspect that biotinidase may have several additional functions. This enzyme may transport free biotin through the bloodstream. It might also have the ability to attach biotin to certain proteins through a process called biotinylation. Within the nucleus, biotinylation of DNA-associated proteins called histones may help determine whether certain genes are turned on or off. It is unclear, however, whether biotinidase plays a role in regulating gene activity.
How are changes in the BTD gene related to health conditions?
Where is the BTD gene located?
Cytogenetic Location: 3p25
Molecular Location on chromosome 3: base pairs 15,601,352 to 15,647,642
(Homo sapiens Annotation Release 107, GRCh38.p2) (
The BTD gene is located on the short (p) arm of chromosome 3 at position 25.
More precisely, the BTD gene is located from base pair 15,601,352 to base pair 15,647,642 on chromosome 3.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about BTD?
You and your healthcare professional may find the following resources about BTD 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 BTD gene or gene products?
See How are genetic conditions and genes named? in the Handbook.
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 BTD?
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (7 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.