Biotinidase (BTD)

Serum biotinidase (BTD; EC 3.5.1.12) catalyzes the hydrolysis of biocytin, a normal product of biotin-dependent carboxylase degradation, to biotin and lysine. The process results in the regeneration of free biotin. Biotin is an essential water-soluble vitamin and is the coenzyme for 4 carboxylases necessary for normal metabolism in humans: pyruvate carboxylase (PCC), propionyl-CoA carboxylase (PCCA), alpha-methylcrotonyl-CoA carboxylase , and acetyl-CoA carboxylase (ACACA).

The deduced 543-amino acid protein has a molecular mass of approximately 57 kD and contains 6 potential N-linked glycosylation sites. Northern blot analysis detected BTD mRNA in human heart, brain, placenta, liver, lung, skeletal muscle, kidney, and pancreas.