Biotinidase

Biotinidase
Identifiers
Symbol	BTD
Entrez	686
HUGO	1122
OMIM	609019
RefSeq	NM_000060
UniProt	P43251
Other data
EC number	3.5.1.12
Locus	Chr. 3 p25

Biotinidase (EC 3.5.1.12, amidohydrolase biotinidase, BTD) is an enzyme that in humans is encoded by the BTD gene.

This enzyme allows the body to use and to recycle the B vitamin biotin, sometimes called vitamin H. Biotinidase extracts biotin from food because the body needs biotin in its free, unattached form. This enzyme also recycles biotin from enzymes in the body that use it as a helper component in order to function. These enzymes, known as carboxylases, are important in the processing of fats, carbohydrates, and proteins. Biotin is attached to these carboxylase enzymes through an amino acid (the building material of proteins) called lysine, forming a complex called biocytin. Biotinidase removes biotin from biocytin and makes it available to be reused by other enzymes.

Biotin, sometimes called vitamin H, is an important water-soluble vitamin that aids in the metabolism of fats, carbohydrates and proteins. The human body cannot produce biotin, but it can obtain it from the diet, internal recycling and at some extent from intestinal bacteria. Biotin deficiency can result in behavioral disorders, lack of coordination, learning disabilities and seizure.

Unlike most vitamins, which are noncovalently bound to enzymes, biotin is chemically linked (covalently bound), and therefore cannot be easily removed from the enzyme denaturation. Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Biotinidase deficiency is an inherited disorder caused by mutations in the BTD gene. When biotinidase activity is deficient, biotin can be neither recycled within the body nor removed from ingested food. Nor can biotin be recycled from enzymes to which it is bound. Deficient biotinidase activity causes specific metabolic enzymes, called carboxylases, to be nonfunctional, inhibiting the proper processing of proteins, fats, and carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin. Approximately 1 in 60,000 newborns are affected by profound (less than 10 percent of normal enzyme activity) or partial (10-30 percent of normal enzyme activity) biotinidase deficiency.

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