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Biotinidase deficiency is an inherited disorder in which the body is not able to process the vitamin biotin properly. Biotin, sometimes called vitamin H, is an important water-soluble vitamin that aids in the metabolism of fats, carbohydrates, and proteins.
How common is biotinidase deficiency?
Approximately 1 in 60,000 newborns are affected by profound (less than 10 percent of normal enzyme activity) or partial (10-30 percent of normal enzyme activity) biotinidase deficiency.
What genes are related to biotinidase deficiency?
Mutations in the BTD gene cause biotinidase deficiency.
Biotinidase is the enzyme that is made by the BTD gene. Many mutations that cause the enzyme to be nonfunctional or to be made at extremely low levels have been identified. Biotin is a vitamin that is chemically bound to proteins. (Most vitamins are only loosely associated with proteins.) Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Another function of the biotinidase enzyme is to recycle biotin from enzymes that are important in metabolism (processing of substances in cells). When biotin is lacking, specific enzymes called carboxylases cannot process proteins, fats, or carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin.
How do people inherit biotinidase deficiency?
This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.
Source: National Institutes of Health
Study results from University Nacional broaden understanding of enzyme research
2009 JAN 5 -- Research findings, 'Impaired biotinidase activity disrupts holocarboxylase synthetase expression in late onset multiple carboxylase deficiency,' are discussed in a new report. According to recent research published in the Journal of Biological Chemistry, "Biotinidase catalyzes the hydrolysis of the vitamin biotin from proteolytically degraded biotin-dependent carboxylases. This key reaction makes the biotin available for reutilization in the biotinylation of newly synthesized apocarboxylases."
"This latter reaction is catalyzed by holocarboxylase synthetase (HCS) via synthesis of 5'-biotinyl-AMP (B-AMP) from biotin and ATP, followed by transfer of the biotin to a specific lysine residue of the apocarboxylase substrate. In addition to carboxylase activation, B-AMP is also a key regulatory molecule in the transcription of genes encoding apocarboxylases and HCS itself. In humans, genetic deficiency of HCS or biotinidase results in the life-threatening disorder biotin-responsive multiple carboxylase deficiency, characterized by a reduction in the activities of all biotin-dependent carboxylases. Although the clinical manifestations of both disorders are similar, they differ in some unique neurological characteristics whose origin is not fully understood. In this study, we show that biotinidase deficiency not only reduces net carboxylase biotinylation, but it also impairs the expression of carboxylases and HCS by interfering with the B-AMP-dependent mechanism of transcription control," wrote A. Pérez-Monjaras and colleagues, University Nacional.
The researchers concluded: "We propose that biotinidase-deficient patients may develop a secondary HCS deficiency disrupting the altruistic tissue-specific biotin allocation mechanism that protects brain metabolism during biotin starvation."
Pérez-Monjaras and colleagues published their study in the Journal of Biological Chemistry (Impaired biotinidase activity disrupts holocarboxylase synthetase expression in late onset multiple carboxylase deficiency. Journal of Biological Chemistry, 2008;283(49):34150-8).
For additional information, contact A. Pérez-Monjaras, Universidad Nacional AutonomadeMexico, Departamento de Biologia Molecular y Biotecnologia, Instituto de Investigaciones Biomedicas, Mexico DF 04510, Mexico.
The publisher's contact information for the Journal of Biological Chemistry is: American Society Biochemistry Molecular Biology Inc., 9650 Rockville Pike, Bethesda, MD 20814-3996, USA.
