RT Journal Article SR Electronic(1) A1 Subramaniam, Prem A1 Bhatnagar, Raj A1 Hooper, Alan A1 Jensen, Roy A.YR 1994 T1 The dynamic progression of evolved character states for aromatic amino acid biosynthesis in Gram-negative bacteria JF Microbiology, VO 140 IS 12 SP 3431 OP 3440 DO https://doi.org/10.1099/13500872-140-12-3431 PB Microbiology Society, SN 1465-2080, AB A systematic analysis of the evolution of aromatic amino acid biosynthesis in the Proteobacteria, previously focussed mainly upon the γ subdivision, has now been extended to the β subdivision. Five lineages were studied, represented by Neisseria gonorrhoeae, Nitrosomonas europaea, Alcaligenes faecalis, rRNA Group-III pseudomonads/Rubrivivax gelatinosus, and rRNA Group-II pseudomonads/Rhodocyclus tenuis.Within the phenylalanine pathway, the bifunctional P-protein (chorismate mutase/prephenate dehydratase) was present in each lineage and must have evolved in a common ancestor of the β and γ subdivisions. Each P-protein was found to be subject to activation by L-tyrosine, and to feedback inhibition by L-phenylalanine. Phenylalanine-inhibited (DS-phe) and tyrosine-inhibited (DS-tyr) isoenzymes of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase probably existed in the common β-subdivision ancestor, with DS-tyr being lost in N. gonorrhoeaeand A. faecalis.The participation of DS-phe in a dissociable multienzyme complex with one or more other common-pathway enzymes is known to exist in N. gonorrhoeae.The same complex is indicated by two peaks of DS-phe seen in chromatographic profiles of Group-III pseudomonads and A. faecalis.It is concluded that the contemporary DS-phe species present in subdivisions γ and β must have had independent origins. Tyrosine biosynthesis was found to be quite diverse within the β subdivision. Nit. europaeapossessed an arogenate dehydrogenase which was specific for NADP+. In all other lineages, a broad-specificity cyclohexadienyl dehydrogenase (CDH) was present. In N. gonorrhoeaethe CDH was specific for NAD+while the remaining CDH species could utilize either NAD+or NADP+. Only the CDH species within the rRNA Group-II pseudomonad/R. tenuislineage was feedback-inhibited by L-tyrosine, and this correlated with an allosteric pattern where activation of the prephenate dehydratase component of the P-protein by L-tyrosine was relatively poor. However, the CDH enzyme present in N. gonorrhoeaeand A. faecaliswas subject to inhibition by 4-hydroxyphenylpyruvate, this being competitive with respect to the cyclohexadienyl substrate. The monofunctional species of chorismate mutase (CM-F) and cyclohexadienyl dehydratase, widely distributed among the γ-subdivision assemblage and recently shown to be periplasmic enzymes, were demonstrated in Pseudomonas pickettii, a member of rRNA homology Group-II., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/13500872-140-12-3431