The synthetic crCD gene combines codon optimization for the C. reinhardtii chloroplast (increasing the codA codon adaptation index from 0.150 to 0.972) with the introduction of three amino acid substitutions that have previously been shown to increase the affinity of the enzyme for 5-FC as a substrate, both in vitro and in E. coli and cancer cell lines (Fuchita et al., 2009). Here, MMP19 is linked to cancer.