Mechanisms of gene transcriptional regulation through biotin and biotin-binding proteins in mammals

Mammals cannot synthesize biotin and depend on a regular dietary supply of this water-soluble vitamin (Zempleni et al., 2009). The Adequate Intake for biotin in adults is 30 µg/d (National Research Council, 1998). The classical role of biotin in mammalian intermediary metabolism is to serve as a covalently bound coenzyme in five carboxylases (Zempleni et al., 2009). Both the cytoplasmic acetyl-CoA carboxylase 1 (ACC1) and the mitochondrial acetyl-CoA carboxylase 2 (ACC2) catalyze the binding of bicarbonate to acetyl-CoA to generate malonyl-CoA, but the two isoforms have distinct functions in intermediary metabolism (Kim et al., 1997). ACC1 produces malonyl-CoA for the synthesis of fatty acid synthesis in the cytoplasm; ACC2 is an important regulator of fatty acid oxidation in mitochondria. The malonyl-CoA produced by ACC2 inhibits mitochondrial uptake of fatty acids for Β-oxidation.