The functionalization of biopolymers with a variety of payloads is a common and well-established strategy to alter their properties, enabling numerous applications such as detection, drug delivery or the immobilization of biological compounds. This technique is particularly used in the oligonucleotide field, as the conjugation of oligonucleotide with polyethylene glycol (PEG), cholesterol or proteins is an effective way to reduce the rapid kidney clearance of oligonucleotides and enhance their pharmacokinetics properties. A common way to improve the delivery of antisense oligonucleotides (ASO) or small interfering RNA (siRNA) to their site of action is their bioconjugation to N-acetylgalactosamine (GalNAc), peptides (in case of cell targeting or cell penetration) or even antibodies. Antibodies properties can themselves be improved by means of bioconjugation. The attachment of one or several drugs to create an antibody drug conjugate (ADC) combines the target specificity of antibodies with the cytotoxic potency of the drug. Despite the rapid expansion of bioconjugates, only a small number of new methods have emerged to improve the chemistry behind the modification of therapeutic proteins. Current methods are mainly based on the reactivity of maleimides and cysteines or Nhydroxysuccinimide esters and lysines. Even if high conjugation yields can be obtained with these techniques, the abundance of cysteines and lysines in a protein sequence makes the number of payloads and the location of the conjugation difficult to control. The absence of regiospecificity in the conjugation reaction leads to a heterogeneous distribution of the payload, potentially resulting in a loss of activity, different therapeutic responses, and a lack of reproducibility. Due to their regio-and stereoselectivity under biologically compatible conditions, enzymes arise as powerful tools for bioconjugation applications. Therefore, the development of a site specific bioconjugation tag, which would be orthogonal to well established approaches and act as a universal tag, would allow the conjugation at defined locations of any protein or peptide scaffold of choice.