Paralogs
Escherichia coli (E. coli) expresses two different forms of shikimate dehydrogenase, AroE and YdiB. Theses two forms are paralogs of each other. The two forms of shikimate dehydrogenase have different primary sequences in different organisms but catalyze the same reactions. The is about 25% similarity between the sequences of AroE and YdiB, but their two structures have similar structures with similar folds. YdiB can utilize NAD or NADP as a cofactor and also reacts with quinic acid. They both have high high affinity of their ligands as shown by their similar enzyme (Km) values. Both forms of the enzyme are independently regulated.
Read more about this topic: Shikimate Dehydrogenase