title: Evolution of the regulatory isozymes of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase present in the Escherichia coli genealogy.
abstract: The evolutionary history of isozymes for 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase has been constructed in a phylogenetic cluster of procaryotes (superfamily B) that includes Escherichia coli. Members of superfamily B that have been positioned on a phylogenetic tree by oligonucleotide cataloging possess one or more of four distinct isozymes of DAHP synthase. DAHP synthase-0 is insensitive to feedback inhibition, while DAHP synthase-Tyr, DAHP synthase-Trp, and DAHP synthase-Phe are sensitive to feedback inhibition by L-tyrosine, L-tryptophan, and L-phenylalanine, respectively. The evolutionary history of this isozyme family can be deduced within superfamily B by using a cladistic methodology of maximum parsimony (R. A. Jensen, Mol. Biol. Evol. 2:92-108, 1985). DAHP synthase-0 was found in Acinetobacter species and in Oceanospirillum minutulum, organisms that also possess DAHP synthase-Tyr. These two isozymes were apparently present in a common ancestor that predated the evolutionary divergence of contemporary superfamily B sublineages. DAHP synthase-0 is postulated to have been the evolutionary forerunner of DAHP synthase-Trp. The newly evolved DAHP synthase-Trp is postulated to have possessed sensitivity to feedback inhibition by chorismate as well as by L-tryptophan, chorismate sensitivity having been retained in rRNA group I pseudomonads (minor sensitivity), group V pseudomonads (very sensitive), and Lysobacter enzymogenes (ultrasensitive). Organisms constituting the enteric lineage of the phylogenetic tree (including a cluster of four Oceanospirillum species) have all lost the chorismate sensitivity of DAHP synthase-Trp. The absence of DAHP synthase-Phe in the Oceanospirillum cluster of organisms supports the previous conclusion that DAHP synthase-Phe evolved recently within superfamily B, being present only Escherichia coli and its close relatives.
authors.forename: S
authors.initials: S
authors.lastname: Ahmad
authors.forename: B
authors.initials: B
authors.lastname: Rightmire
authors.forename: R A
authors.initials: RA
authors.lastname: Jensen
mesh_terms: D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000032:analysis*; D000446:Aldehyde-Lyases / Q000032:analysis*; D005075:Biological Evolution; D004926:Escherichia coli / Q000201:enzymology*; D007527:Isoenzymes / Q000032:analysis*; D010649:Phenylalanine; D013139:Spirillum / Q000201:enzymology; D014364:Tryptophan; D014443:Tyrosine
chemical_list: D007527:Isoenzymes; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D000446:Aldehyde-Lyases