BTD, also known as biotinidase isoform 1, is a member of the nitrilase superfamily, which consists of 12 families of nitrilases, amidases, carbamylases, and N-acyltrasferases. It catalyzes the hydrolysis of biocytin, the product of biotin-dependent carboxylase degradation, to biotin and lysine. It may have an important regulatory role in chromatin/DNA function. Recombinant human BTD, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.