BiotinylAMP

BiotinylAMP, or biotinyl-5'-adenylate, is a reactive biochemical intermediate formed during the activation of biotin by the enzyme biotin ligase (BirA). In this form, biotin is linked to an adenosine monophosphate moiety via a phosphodiester bond at the 5' position of the ribose. BiotinylAMP is typically a transient species that participates in the transfer of biotin to a target protein rather than existing as a stable, free product.

Biological role

In bacteria, BirA catalyzes the ATP-dependent activation of biotin to biotin-5'-AMP. This activated intermediate then transfers biotin to a specific lysine residue on the biotin carboxyl carrier protein (BCCP), a component of the acetyl-CoA carboxylase complex. After the transfer, the reaction releases AMP and yields a biotinylated protein, enabling the carboxylation reactions essential for fatty acid synthesis and other metabolic pathways. The biotinyl-AMP step is thus central to the regulation and execution of protein biotinylation in vivo.

Laboratory context and applications

Biotinyl-AMP is also relevant in laboratory studies of biotinylation mechanisms. BirA-based systems are widely used for site-specific protein labeling, including in vitro biotinylation of proteins bearing a suitable biotin acceptor sequence (such as AviTag). In these experimental contexts, biotin is activated by BirA to generate biotin-5'-AMP, which then transfers biotin to the acceptor lysine. Because biotinyl-AMP is highly reactive and short-lived, it is usually not isolated as a stable reagent but is generated in situ during the labeling reaction.

Properties

Biotinyl-AMP is a labile intermediate that readily participates in biotin transfer reactions and hydrolyzes to biotin and AMP if not immediately utilized. Its transient nature reflects its role as an activated carrier rather than a standalone metabolite.