| Type: | Family | Name: | Bifunctional ligase/repressor BirA |
| Description: | BirA acts both as a biotin ligase and a biotin-operon repressor. In the presence of ATP, BirA activates biotin to form the BirA-biotinyl-5'-adenylate (BirA-bio-5'-AMP) or holoBirA complex. HoloBirA can either transfer the biotinyl moiety to the biotin carboxyl carrier protein (BCCP) subunit of acetyl-CoA carboxylase, or bind to the biotin operator site and inhibit transcription of the operon [, , , ]. The switch between the enzymatic activity and the repressor activity of BirA is regulated by cellular demand for biotin. In conditions of high biotin demand, holoBirA associates with apoBCCP and transfers biotin from bio-5'-AMP to apoBCCP. In conditions of low biotin demand, holoBirA dimerises and binds the biotin operator []. | Short Name: | Bifunct_BirA |
