Cytosine deaminase mutant and application thereof in methylation detection

The invention provides a cytosine deaminase mutant APOBEC mut5, a coding nucleotide sequence of the cytosine deaminase mutant APOBEC mut5, an application of the cytosine deaminase mutant APOBEC mut5 in methylation detection, and a methylation detection method based on the APOBEC mutant, which is called as beta FDM-seq. According to the beta FDM-seq, firstly, normal C is changed into 5cxmC by using a methyltransferase mutant M.MpeI N374K and carboxyl-S-adenosine-L-methionine, then 5mC is changed into T by using APOBEC mut5, 5hmC and 5cxmC are not subjected to deamination, a 5mC functional site can be found through NGS library-building sequencing and bioinformatics analysis on a transformed DNA fragment, and the beta FDM-seq has a huge clinical application value. The initial template quantity of the beta FDM-seq is as low as 10 ng, the single-base resolution ratio is achieved, the positive site detection rate is 99.0% or above, the accuracy is high, the template damage is small, the data quality is high, and th