Members of the adenosine deaminase acting on RNA (ADAR) family of enzymes consist of double-stranded RNA-binding domains (dsRBDs) and a deaminase domain (DD) that converts adenosine (A) into inosine (I), which acts as guanosine (G) during translation. Using the MS2 system, we engineered the DD of ADAR1 to direct it to a specific target. The aim of this work was to compare the deaminase activities of ADAR1-DD and various isoforms of ADAR2-DD.