Figure 7. The complex evolutionary history of the heme biosynthesis pathway is reflected in high replaceability across species.
In eukaryotes, heme biosynthesis enzymes have been replaced historically by endosymbiosis events from bacteria, leading to higher similarity across these lineages, while the archaeal pathway appears to be more divergent (Storbeck et al., 2010). Following the endosymbiosis of the cyanobacterial chloroplast, plants adopted most of the chloroplast-derived heme biosynthesis genes, losing many ancestral eukaryotic heme pathway genes (Oborník and Green, 2005). Yeast and humans both retain the predicted ancestral eukaryotic heme biosynthesis pathway. While enzymatic steps are mostly shared between yeast, plants, bacteria, and humans, localization of individual proteins differs substantially between species. Asterisks indicate results curated from literature.