Lys O BCCP Figure 28.40 • Coenzyme form of biotin.
the case of two identified genetic disorders. Holocarbo-xylase deficiency is a genetic disorder of biotin-(propionyl-CoA-carboxylase [ATP-hydrolysing]) ligase, the enzyme responsible for the terminal step incorporating biotin into the apoenzyme. Biotinidase (EC 188.8.131.52) deficiency is a genetic disorder of the amidase that releases biotin from the apoenzyme and allows it to be recycled. Both of these lead to multiple carboxylase deficiency (MCD), a condition marked by decreased activity of all biotin-dependent car-boxylases and both respond, at least partially, to large doses of biotin.197 The symptoms of biotin deficiency include dermatitis, conjunctivitis, alopecia, and CNS abnormalities including behavioral, developmental, and psychological effects.198
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