Biotinidase

Biotinidase is a human enzyme that is produced according to the instructions of the BTD gene. This enzyme allows the body to use and to recycle the B vitamin biotin, sometimes called vitamin H. Biotinidase removes 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.

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

Unlike most vitamins, which are noncovalently bound to proteins, biotin is chemically linked (covalently bound), and therefore cannot be separated by protein denaturation or shifts in conformation. 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.