Biotin metabolism

On rare occasions an organic aciduria occurs not because of an enzyme deficiency but from a failure to transport or activate a water-soluble vitamin that serves as a cofactor for the reaction in question. Thus, congenital deficiencies in the metabolism of vitamin B12 commonly give rise to methylmalonic aciduria (Fig. 40-1, Table 40-2). Similarly, deficiencies of biotin metabolism can cause a severe organic aciduria (Table 40-2). It is very important to be aware of the defects of vitamin metabolism because the administration of large doses of these cofactors may completely prevent brain damage. 

Biotin metabolism Folate biosynthesis One carbon pool by folate Retinol metabolism Porphyrin and chlorophyll metabolism Terpenoid biosynthesis Xenobiotics metabolism Ubiquinone biosynthesis Flavonoids, stilbene, and lignin biosynthesis... 

Baumgartner ER, Suormala T (1997) Multiple carboxylase deficiency inherited and acquired disorders of biotin metabolism. Int J Vitam Nutr Res 67 377-384... 

Wolf (2001) Disorders of biotin metabolism. In Scriver CR, Beaudet AL, Sly VS, Valle D (eds) The Metabolic and Molecular Basis of Inherited Disease. McGraw-Hill, New York, pp 3935-3962... 

Deficiency can be due to two known genetic disorders of biotin metabolism or be induced by excess intake of avidin, which binds biotin and thus leads to poor absorption. Symptoms are alopecia, eczema around nose and mouth, conjunctivitis, hyperaesthesia, paraesthesia, depression, and muscle pain 29 The recommended daily allowance is 30 to 35 fig.112... 

Hymes J, Wolf B Biotinidase and its roles in biotin metabolism. Clin ChimActa 255 1-11,1996. 

Wolf B Disorders of biotin metabolism treatable neurological syndromes, in Rosenberg R, Prusiner SB, DiMauro S, Barchi RL, Kunkel LM (eds) The Molecular and Genetic Basis of Neurological Disease. Butterworth, Stoneham, MA, 1992b, pp. 569-81. 

Baumgartner ER and Suormala T (1999) Inherited defects of biotin metabolism. Biofactors 10, 287-90. 

Description. Also known as vitamin Bg or H, this vitamin is of great importance for the biochemistry of the human organism. Biotin is the cofactor for a small group of enzymes that catalyze carboxyla-tion, decarboxylation, and transcarboxylation reactions in carbohydrate and fatty acid metabolism. Deficiency of this vitamin is rare in humans, but can be induced in special circumstances in individuals with inborn errors of biotin metabolism, in individuals taking certain medications, and in some women during pregnancy. ... 

Gravel, R.A., and Narang, M.A., 2005. Molecular genetics of biotin metabolism old vitamin, new science. The Journal of Nutritional Biochemistry. 16 428 31. 

Mock, D.M., Mock, N.I., Nelson, R.P., and Lombard, K.A., 1998. Disturbances in biotin metabolism in children undergoing long-term anticonvulsant therapy. Journal of Pediatric Gastroenterology and Nutrition. 26 245-250. 

Gravel R and Narang M. Molecular genetics of biotin metabolism Old vitamins, new science. J. Nutr. Biochem. 16 428-431 (2005). 

High clinical suspicion for organic acid disorders with possibly isolated elevations of pathological metabolites in CSF ( cerebral lactic addemiasj glutaryl-CoA dehydrogenase deficiency disorders of biotin metabolism)... 

Mock has described a very sensitive method (the limit of detection is around 5 fmol) for the detection of biotin and its metabolites, involving C18 reversed-phase HPLC separation followed by detection using an avidin-horseradish peroxidase conjugate (92). The principle of this method has already been discussed. This methodology has allowed the identification and quantification of biotin, bisnorbi-otin, biotin sulfoxides, and biotin sulfone in human and animal serum and urine. Furthermore, new biotin metabolites (tetranorbiotin sulfoxide and bisnorbiotin methyl ketone) were detected in human urine (114). This technique should potentiate more accurate studies on human biotin metabolism (see, e.g., 115). 

This review is dedicated to Michel Gaudry (1942-1998), who contributed to many aspects in the research field of biotin biochemistry (biotin metabolism, biotin transport, biotin deficiency, and so on). His outstanding contribution to the previous editions of this book chapter is gratefully acknowledged. 

KS Wang, A Patel, DM Mock. The metaboUte profile of radioisotope-labeled biotin in rats indicates that rat biotin metabolism is similar to that of humans. J Nutr 126 ... 

J Hymes, B Wolf. Biotinidase and its role in biotin metabolism. Clin Chim Acta 255 1-11, 1995. 

Figure 1 Biotin metabolism and degradation. Ovals denote enzymes or enzyme systems rectangles denote biotin, intermediates, and metabolites. AMP, adenosine monophosphae ATP, adenosine triphosphate CoA, coenzyme A Ppi, pyrophosphate , site of attachment of carboxyl moiety.

Few cases of biotin delidency have been reported in humans. There are some rare congenital disorders of biotin metabolism. However, it has been shown to occur... 

The toxicity of biotin is low and doses of up to 200 mg per day are tolerated by those with hereditary disorders in biotin metabolism and doses of 5 mg per day have tolerated long term by non-deficient subjects. 

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