CT0225 aroC*D (DEFINITION: dehydroquinate dehydratase and shikimate dehydrogenase) is a biofunctional enzyme which is homologous to the pirS46210 dehydroquinase shikimate dehydrogenase from Common tobacco. The bifunctional aroC*D is very interesting because it would be the first bacterial example of a bifunctional protein similar to what plants have. Plants in general have the aroC and aroD enzymic activities fused into a single bifunctional protein. Likely scenario: the bifunctional protein arose in a bacterium in the Chlamydia lineage. A member of this group established an endosymbiotic relationship with an organism in the plant lineage, and the gene was incorporated into the plant genome.

We found most of the "eukaryotic" protein of chlamydia not appear to be specifically related to their animal homologs. Unexpectedly, they tend to group with plant proteins in phylogenetic analyses. This might suggests that chlamydiase have been intracellular parasites of vertebrates for a while of their evolutionary history. The endosymbiotic theory of eucaryotic evolution might explain the cases above, Such as moden plant cell evolved in steps through the incorporation into cells from the chlamydia eg., aroC*D case. For more information about this topic, check the NCBI coffeebreak page.