Evolution and phylogenetic distribution of the specialized isozymes of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase in superfamily-B prokaryotes.

Purple sulphur (Superfamily B) bacteria vary greatly in the isozyme number and regulatory properties corresponding to the initial step of aromatic amino acid biosynthesis, 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase. The signal evolutionary events that are responsible for generation of the three regulatory isozymes of DAHP synthase found in the contemporary Escherichia coli and other enteric bacteria have been deduced, starting from a common ancestor of all Superfamily-B organisms. This analysis of one prokaryotic grouping is a model for analogous studies of the evolutionary history of other biochemical pathways. It is also the beginning of an analysis that can be extended to include the entire assemblage of prokaryotic organisms.