Study note
BiochemistryMicronutrients: Vitamins & Minerals

Biotin in carboxylation and cell-cycle regulation

THE CONTEXT
Biotin serves as a carbon dioxide carrier in a small group of carboxylase reactions.

Biotin-dependent enzymes

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Biotin transfers carbon dioxide in reactions catalyzed by acetyl-CoA carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase, and methylcrotonyl-CoA carboxylase.

Attachment and reaction sequence

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Holocarboxylase synthetase transfers biotin onto a lysine residue of the apoenzyme, forming the biocytin residue of the holoenzyme.
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The reactive intermediate, 1-N-carboxybiocytin, forms from bicarbonate in an ATP-dependent reaction.
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The carboxyl group is then transferred to the substrate for carboxylation.

Additional cellular role

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Biotin also participates in cell-cycle regulation by biotinylating key nuclear proteins.
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