Abstract: Proposed are an adenine base editor having increased thymine-cytosine sequence-specific cytosine base editing activity, a cytosine base editing method, and a cytosine base editing kit. The editor, produced by introducing a P48R mutation into an adenosine deaminase, has an operating range that is more sophisticated than conventional cytosine base editors, allows cytosine base editing only when cytosine is positioned right behind thymine, thereby enabling elaborate editing even when there is a plurality of cytosines within the range, and enables cytosine to be substituted with thymine or guanine in the presence or absence of UGI, respectively. Therefore, the cytosine base editing composition can be effectively used in the fields of gene therapy or new crop development which requires precise editing of only cytosine in all living organisms, including humans, plants, and bacteria.

Abstract: The present invention relates to an adenine base editor from which cytosine editing activity is removed, a method of editing an adenine base, and method of editing an adenine base. In the present invention, it was confirmed that four mutations (V106W, D108Q, F148A and F149A) in adenosine deaminase increase the specificity for adenine editing by reducing cytosine base editing efficiency, and ABE variants were manufactured by introducing respective mutations into a variety of more improved adenine base editors than ABEmax, and tested, confirming that the mutations significantly decrease a cytosine editing effect. Therefore, the adenine base editor according to the present invention is able to more accurately edit adenine, and the method of editing an adenine base can be effectively used in the field of gene therapy that has to accurately edit only adenine in all living organisms including humans, plants and bacteria or novel crop development.