ADAR, or Adenosine Deaminase Acting on RNA, is an enzyme that plays a crucial role in the editing of RNA molecules. It specifically converts adenosine residues in RNA to inosine, which can alter the function and stability of the RNA. This process is important for various cellular functions, including the regulation of gene expression and the immune response. The activity of ADAR is particularly significant in the context of RNA viruses, as it can influence how these viruses replicate and evade the immune system. Mutations in the ADAR gene have been linked to several diseases, highlighting its importance in maintaining cellular health and function.