Partial Biotinitase Deficiency, 23andme Test, BTD GENE POLL? What Genes are related to the biotinidase deficiency? Mutations in the BTD gene cause biotinidase deficiency. The BTD gene provides instructions for making an enzyme called biotinidase. This enzyme helps the body reuse 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 break down fats, proteins, and carbohydrates effectively. Biotinidase also recycles biotin within the body. Mutations in the BTD gene reduce or eliminate the activity of biotinidase. Profound biotinidase deficiency results when the activity of biotinidase is reduced to less than 10 percent of normal. Partial biotinidase deficiency occurs when biotinidase activity is reduced to between 10 percent and 30 percent of normal. Without enough of this enzyme, biotin cannot be separated from proteins or recycled normally. As a result, the body is less able to process important nutrients. These defects underlie the potentially serious medical problems associated with biotinidase deficiency. Partial biotinidase deficiency is a milder form of this condition.