Biotinidase Deficiency Essay, Research Paper

Biotinidase Deficiency

Biotinidase deficiency is an inherited metabolic disorder which prevents the body from processing biotin in a normal manner. It was not discovered until 1983 (Thibodeau, Wolf, 1999),# therefore no long term research on the disease has been done. Children with the disease are given large doses of free biotin which alleviates present symptoms of the disease and prevents new symptoms from developing. So far no long term side effects of the treatment have been discovered and children with the disorder are expected to have a normal lifespan. #

This is an autosomal recessive disorder, which means that the gene that causes it is on an antosome rather than a sex chromosome. therefore, one must inherit the defective gene from both parents to have the disorder (Thiodeau, Wolf, 1999). in other words, both parents must be carriers or have the disorder themselves in order to pass it on to their child. The gene that causes this biotinidase deficiency is found on the short arm of chromosome 3. Fourty different mutations have been that can cause biotinidase deficiency have been documented (Thibodeau, Wolf, 1999). In one study four mutations were shown to occur in 59% of children diagnosed with biotinidase deficiency. two of these mutations occurred in both children diagnosed though screening at birth and in children diagnosed by symptoms which developed over time; however, they occurred in the symptomatic population much more often. because the other two mutations only occurred in children diagnosed by screening, it is thought that they would not develop symptoms even with treatment (Wolf, B. 2000).

People with biotinidase deficiency have insufficient biotinidase activity. Carriers (peopel with one defective gene) have 50% of regular biotinidase activity and nomally do not have any of the symptoms of biotinidase deficiency. people with partial biotinidase deficiency have 10-30% of normal activity, while people with profound biotinidase activity have less than 10% of biotinidase activity (Thibodeau, Wolf 1999). Biotin is a vitamin found in many foods that is used by carboxylases enzymes to produse some fats and carbohydrates and to breakdown proteins. biotin in foods is normally bound to protien and is unusable. biotinidase separates the biotin from the protein in order for it to be used by the carboxylases and then lets the biotin be reused so that we do not need to eat large amounts of biotin in our diet. free biotin attaches to the amino acid, lysine, on inactive carboxylases. the carboxylases are then broken down, but the biotin stays attached to the lysine to form biocytin. the biocytin is then broken down by biotinidase and the biotin is reused. when biotinidase activity is not sufficient for the carboxylases to perform their normal functions, and harmful by-products build up in the body. The body is also unable to recycle the free biotin that it has, therefore it needs to be supplied with much more than normal (Thibodeau, Wolf, 1999).