APOBEC3A (A3A) can be used in the detection of 5-methylcitosine (5mC) as part of the enzymatic methyl sequencing (EM-seq) pipeline. To improve EM-seq pipeline, A3A was rationally mutated with the H29R mutation to theoretically improve the pH sensitivity of A3A. The H29R mutation was found to be ineffective. While studying the H29R mutation, new methods for the expression of cytotoxic enzymes were tested for the expression of A3A. The H29R construct was expressed with a split-GFP, allowing the protein to be expressed as two inactive halves. In parallel, A3A was also expressed as an intein for intein ligation, allowing for the enzyme to be expressed as two inactive halves. Both methods successfully increased the yield of the enzymatic expressions of A3A. Intein ligation was also tested for the expression of large cell penetrating Cas9 peptides as a part of Peptide Assisted Genome Editing (PAGE) in preparation for the addition of base editors to these gene editing complexes. Scar tolerance for the cell penetrating peptides was confirmed and the use of inteins for the expression of cell penetrating peptides continues to be an area of study. All work done for this thesis was performed in the Kohli lab at the University of Pennsylvania.