HomeGeneticsGeneBTD gene
Back to Gene
BTD gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

BTD gene

The BTD gene provides instructions for making the enzyme biotinidase, which is essential for recycling biotin and supporting critical cellular functions.

Normal Function

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.

Health Conditions Related to Genetic Changes

Biotinidase deficiency

More than 150 mutations in the BTD gene have been identified in people with biotinidase deficiency. This disorder, if untreated, can affect many parts of the body and cause delayed development. Most of the mutations that cause biotinidase deficiency change single amino acids in the biotinidase enzyme. These changes occur in critical regions of the enzyme and reduce or eliminate the enzyme's activity.

  • Profound biotinidase deficiency: This severe form results when the activity of biotinidase is reduced to less than 10 percent of normal.
  • Partial biotinidase deficiency: These mutations reduce biotinidase activity to between 10 percent and 30 percent of normal.

Without enough of this enzyme, biotin cannot be recycled. The resulting shortage of free biotin impairs the activity of biotin-dependent carboxylases, leading to a buildup of potentially toxic compounds in the body. If the condition is not treated promptly, this buildup damages various cells and tissues, causing the signs and symptoms associated with biotinidase deficiency.

Leigh syndrome

MedlinePlus Genetics provides information about Leigh syndrome.

Frequently Asked Questions

There are generally no strict dietary restrictions for individuals with biotinidase deficiency who are taking biotin supplements. A balanced diet that includes natural sources of biotin, such as eggs, liver, and milk, is safe and encouraged. The primary focus is on maintaining the daily biotin supplement regimen. However, caregivers should ensure that the child is not consuming excessive amounts of raw egg whites, as they contain a protein called avidin that binds to biotin and can interfere with its absorption, potentially reducing the effectiveness of the treatment.
Biotinidase deficiency is inherited in an autosomal recessive pattern, meaning a child must inherit two mutated copies of the BTD gene, one from each parent, to have the condition. Parents who are carriers typically do not show symptoms. If a child is diagnosed, both parents are likely carriers, and there is a 25 percent chance with each subsequent pregnancy that another child will be affected. Genetic counseling is recommended for the family to discuss the risks and to offer carrier testing to other at-risk relatives.
Diagnosis is usually confirmed through newborn screening, which measures biotinidase enzyme activity in blood samples. If an infant is not screened or if symptoms develop later, clinicians may order specific blood and urine tests to check for elevated levels of organic acids and amino acids. Early warning signs in untreated infants can include hair loss (alopecia), skin rashes, hearing loss, and developmental delays. Because these symptoms can mimic other conditions, any infant showing unexplained hair thinning or failure to thrive should be evaluated for metabolic disorders.
Biotinidase deficiency is a lifelong genetic condition, but it is highly treatable and manageable with daily oral biotin supplements. Unlike some other metabolic disorders, the treatment is very effective; most patients who begin supplementation early can achieve normal development and avoid severe neurological damage. The enzyme itself cannot be replaced, but providing high doses of free biotin bypasses the need for the body to recycle it, allowing biotin-dependent enzymes to function normally. Consistent daily adherence to the supplement is critical to prevent a recurrence of symptoms.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss