Prephenate aminotransferase directs plant phenylalanine biosynthesis via arogenate

Journal name:
Nature Chemical Biology
Volume:
7,
Pages:
19–21
Year published:
DOI:
doi:10.1038/nchembio.485
Received
Accepted
Published online
Corrected online

The aromatic amino acids L-phenylalanine and L-tyrosine and their plant-derived natural products are essential in human and plant metabolism and physiology. Here we identified Petunia hybrida and Arabidopsis thaliana genes encoding prephenate aminotransferases (PPA-ATs), thus completing the identification of the genes involved in phenylalanine and tyrosine biosyntheses. Biochemical and genetic characterization of enzymes showed that PPA-AT directs carbon flux from prephenate toward arogenate, making the arogenate pathway predominant in plant phenylalanine biosynthesis.

At a glance

Figures

  1. Effects of PPA-AT downregulation on the shikimate, phenylalanine and tyrosine pathways.
    Figure 1: Effects of PPA-AT downregulation on the shikimate, phenylalanine and tyrosine pathways.

    (a) Proposed phenylalanine and tyrosine biosynthetic pathways in plants. Multiple enzymatic steps involved are shown by dotted lines. ADH, arogenate dehydrogenase; ADT, arogenate dehydratase; CM, chorismate mutase; E4P, erythrose 4-phosphate; HPP-AT, 4-hydroxyphenylpyruvate aminotransferase; PDH, prephenate dehydrogenase; PDT, prephenate dehydratase; PEP, phosphoenolpyruvate; PPA-AT, prephenate aminotransferase; PPY-AT, phenylpyruvate aminotransferase. (b) PPA-AT RNAi suppression in petunia petals. The levels of PhPPA-AT mRNA (n = 4 biological replicates), PPA-AT activity (n = 4), plastidial ADT activity (n = 3), aromatic amino acids phenylalanine, tyrosine and tryptophan (n ≥ 6) and the pathway intermediates, prephenate, arogenate and shikimate (n ≥ 6), in the petals of PPA-AT RNAi lines (F, S and Z) relative to corresponding levels in control (Co), which were set as 100% (2.9 and 0.14 nmol s−1 per milligram protein for PPA-AT and ADT activities, respectively; 317.6, 8.2, 18.0, 5.4, 26.1, 64.9 nmol per gram fresh weight for phenylalanine, tyrosine, tryptophan, prephenate, arogenate and shikimate, respectively). Data are means ± s.e.m. Asterisks indicate statistically significant differences in transgenics relative to control (P < 0.05, two-tailed Student's t-test).

  2. PPA-AT converts prephenate to arogenate.
    Figure 2: PPA-AT converts prephenate to arogenate.

    Incubation of the recombinant PhPPA-AT enzyme with prephenate, aspartate and pyridoxal phosphate led to the production of arogenate (peak 3 in the middle panel), which was converted to phenylalanine (peak 4 in the lower panel) by acid treatment. These amino acids as well as standards (the upper panel) were derivatized by o-phthalaldehyde (OPA) before HPLC analysis. OPA-derivatized arogenate and phenylalanine peaks from the enzyme reaction (peaks 3 and 4, respectively) showed identical MS spectra to those of standards (peaks 1 and 2, respectively; Supplementary Fig. 5).

Change history

Corrected online 10 December 2010
In the version of this article initially published, the word “prephenate” was inadvertently switched to “phenylalanine” in the eighth paragraph. The error has been corrected in the HTML and PDF versions of the article.

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Affiliations

  1. Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, USA.

    • Hiroshi Maeda,
    • Heejin Yoo &
    • Natalia Dudareva

Contributions

H.M. and N.D. designed research; H.M. and H.Y. performed experiments; H.M., H.Y. and N.D. analyzed data; H.M. and N.D. wrote the paper. All authors read and edited the manuscript.

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The authors declare no competing financial interests.

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Supplementary information

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  1. Supplementary Text and Figures (1M)

    Supplementary Methods, Supplementary Figures 1–9 and Supplementary Tables 1 & 2

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  1. Supplementary Data Set (41K)

    Supplementary Data Set

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