Biochemical characterization of TyrA enzymes from Ignicoccus hospitalis and Haemophilus influenzae: A comparative study of the bifunctional and monofunctional dehydrogenase forms

Shlaifer, Irina; Quashie, Peter K.; Kim, Ho; Turnbull, Joanne L.

doi:10.1016/j.bbapap.2016.12.014

Cited by 1 publication

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“…MhTyrA was chosen as no TyrAs from its subclade of clade II have previously been characterized (Figure 2 ). Also, MhTyrA is a monofunctional enzyme, while some archaea, fungi, and γ-proteobacteria orthologs in clade II are bifunctional and have a chorismate mutase enzyme domain (Hudson et al, 1984 ; Shlaifer et al, 2017 ). MhTyrA was expressed in E. coli and the recombinant enzyme was purified to homogeneity using affinity-chromatography (Figure S3 ) and used for biochemical analyses.…”

Section: Resultsmentioning

confidence: 99%

Conserved Molecular Mechanism of TyrA Dehydrogenase Substrate Specificity Underlying Alternative Tyrosine Biosynthetic Pathways in Plants and Microbes

Schenck

Men

Maéda

2017

Front. Mol. Biosci.

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L-Tyrosine (Tyr) is an aromatic amino acid synthesized de novo in plants and microbes. In animals, Tyr must be obtained through their diet or synthesized from L-phenylalanine. In addition to protein synthesis, Tyr serves as the precursor of neurotransmitters (e.g., dopamine and epinephrine) in animals and of numerous plant natural products, which serve essential functions in both plants and humans (e.g., vitamin E and morphine). Tyr is synthesized via two alternative routes mediated by a TyrA family enzyme, prephenate, or arogenate dehydrogenase (PDH/TyrAp or ADH/TyrAa), typically found in microbes and plants, respectively. Although ADH activity is also found in some bacteria, the origin of arogenate-specific TyrAa enzymes is unknown. We recently identified an acidic Asp222 residue that confers ADH activity in plant TyrAs. In this study, structure-guided phylogenetic analyses identified bacterial homologs, closely-related to plant TyrAs, that also have an acidic 222 residue and ADH activity. A more distant archaeon TyrA that preferred PDH activity had a non-acidic Gln, whose substitution to Glu introduced ADH activity. These results indicate that the conserved molecular mechanism operated during the evolution of arogenate-specific TyrAa in both plants and microbes.

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Section: Resultsmentioning

confidence: 99%