Chapter 33 - Disorder: Biotin: Biotinidase deficiency and holocarboxylase synthetase deficiency

Abstract

Multiple carboxylase deficiency is caused by either biotinidase deficiency (BTD, OMIM # 253260) or holocarboxylase synthetase deficiency (HLCSD, OMIM # 253270). Both these enzymes deliver biotin to multiple biotin-dependent carboxylases and are required for the recycling and re-utilization of biotin and the proper functioning of the biotin-dependent carboxylases. Biotinidase (EC3.5.1.12) is the enzyme that frees biotin from its protein conjugates to allow it to be recycled for use. Holocarboxylase synthetase (EC6.3.4.10) is the enzyme that catalyzes the covalent binding of biotin with the four apocarboxylases to form the active carboxylases. These carboxylases are involved in gluconeogenesis, fatty acid synthesis, and several catalytic pathways for amino acids and odd-chain fatty acids.