Aromatic amino acid aminotransferases in plants

Wang, Minmin; Maéda, Hiroshi

doi:10.1007/s11101-017-9520-6

Cited by 30 publications

(27 citation statements)

References 198 publications

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“…Aspartate is one of the major amino donors of many aminotransferase enzymes, which plays central roles in nitrogen metabolic network and hence synthesis of many nitrogen‐containing metabolites including amino acids (Toney, ; Wang and Maeda, ). For example, aspartate is the main amino donor of prephenate aminotransferase, which catalyzes the preceding step of TyrA dehydrogenases (Graindorge et al ., ; Maeda et al ., ; Dal Cin et al ., ; Figure ).…”

Section: Discussionmentioning

confidence: 99%

Imbalance of tyrosine by modulating TyrA arogenate dehydrogenases impacts growth and development of Arabidopsis thaliana

et al. 2019

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L-Tyrosine is an essential aromatic amino acid required for the synthesis of proteins and a diverse array of plant natural products; however, little is known on how the levels of tyrosine are controlled in planta and linked to overall growth and development. Most plants synthesize tyrosine by TyrA arogenate dehydrogenases, which are strongly feedback-inhibited by tyrosine and encoded by TyrA1 and TyrA2 genes in Arabidopsis thaliana. While TyrA enzymes have been extensively characterized at biochemical levels, their in planta functions remain uncertain. Here we found that TyrA1 suppression reduces seed yield due to impaired anther dehiscence, whereas TyrA2 knockout leads to slow growth with reticulate leaves. The tyra2 mutant phenotypes were exacerbated by TyrA1 suppression and rescued by the expression of TyrA2, TyrA1 or tyrosine feeding. Low-light conditions synchronized the tyra2 and wild-type growth, and ameliorated the tyra2 leaf reticulation. After shifting to normal light, tyra2 transiently decreased tyrosine and subsequently increased aspartate before the appearance of the leaf phenotypes. Overexpression of the deregulated TyrA enzymes led to hyper-accumulation of tyrosine, which was also accompanied by elevated aspartate and reticulate leaves. These results revealed that TyrA1 and TyrA2 have distinct and overlapping functions in flower and leaf development, respectively, and that imbalance of tyrosine, caused by altered TyrA activity and regulation, impacts growth and development of Arabidopsis. The findings provide critical bases for improving the production of tyrosine and its derived natural products, and further elucidating the coordinated metabolic and physiological processes to maintain tyrosine levels in plants.

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Section: Discussionmentioning

confidence: 99%

Imbalance of tyrosine by modulating TyrA arogenate dehydrogenases impacts growth and development of Arabidopsis thaliana

et al. 2019

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“…2A). In most plant species, TAT catalyzes the removal of the amino group of tyrosine (Wang et al 2016(Wang et al , 2019Wang and Maeda 2018). An exception is that in legumes, which have a non-plastidic prephenate dehydrogenase (PDH, EC 1.3.1.13) that converts prephenate into pHPP, TAT is assumed to catalyze the transamination of pHPP to synthesize tyrosine (Schenck et al 2015).…”

Section: The General Tyrosine Metabolism Pathwaymentioning

confidence: 99%

General and specialized tyrosine metabolism pathways in plants

Fang

et al. 2019

aBIOTECH

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The tyrosine metabolism pathway serves as a starting point for the production of a variety of structurally diverse natural compounds in plants, such as tocopherols, plastoquinone, ubiquinone, betalains, salidroside, benzylisoquinoline alkaloids, and so on. Among these, tyrosine-derived metabolites, tocopherols, plastoquinone, and ubiquinone are essential to plant survival. In addition, this pathway provides us essential micronutrients (e.g., vitamin E and ubiquinone) and medicine (e.g., morphine, salidroside, and salvianolic acid B). However, our knowledge of the plant tyrosine metabolism pathway remains rudimentary, and genes encoding the pathway enzymes have not been fully defined. In this review, we summarize and discuss recent advances in the tyrosine metabolism pathway, key enzymes, and important tyrosine-derived metabolites in plants.

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“…The reaction is mediated by Tyr aminotransferases (TATs, 2 EC 2.6.1.5), which catalyze the reversible reaction between Tyr and 4-hydroxyphenylpyruvate (HPP). In most microbes, HPP is the intermediate of the Tyr biosynthetic pathway, and TATs are usually responsible for the final step of Tyr biosynthesis from HPP (24,25). Indeed, knockout mutants of TATs in microbes often exhibit Tyr auxotrophy (26 -28).…”

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“…Virus-induced silencing of TAT in Papaver somniferum led to reduction in the levels of isoquinoline alkaloids derived from both HPP and Tyr (53). Arabidopsis possesses at least two homologous TAT enzymes, TAT1 and TAT2 (At5g53970 and At5g36160, respectively (45,54,55)), although additional aminotransferases having TAT activity are likely present (25). The TAT1 enzyme prefers Tyr as an amino donor substrate, has a low K m toward Tyr, and favors Tyr deamination to form HPP rather than the reverse reaction.…”

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TAT1 and TAT2 tyrosine aminotransferases have both distinct and shared functions in tyrosine metabolism and degradation in Arabidopsis thaliana

Wang

Toda

Block

et al. 2019

Journal of Biological Chemistry

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Edited by F. Peter Guengerich Plants produce various L-tyrosine (Tyr)-derived compounds that are critical for plant adaptation and have pharmaceutical or nutritional importance for human health. Tyrosine aminotransferases (TATs) catalyze the reversible reaction between Tyr and 4-hydroxyphenylpyruvate (HPP), representing the entry point in plants for both biosynthesis of various natural products and Tyr degradation in the recycling of energy and nutrients. To better understand the roles of TATs and how Tyr is metabolized in planta, here we characterized single and double loss-of-function mutants of TAT1 (At5g53970) and TAT2 (At5g36160) in the model plant Arabidopsis thaliana. As reported previously, tat1 mutants exhibited elevated and decreased levels of Tyr and tocopherols, respectively. The tat2 mutation alone had no impact on Tyr and tocopherol levels, but a tat1 tat2 double mutant had increased Tyr accumulation and decreased tocopherol levels under highlight stress compared with the tat1 mutant. Relative to WT and the tat2 mutant, the tat1 mutant displayed increased vulnerability to continuous dark treatment, associated with an early drop in respiratory activity and sucrose depletion. During isotope-labeled Tyr feeding in the dark, we observed that the tat1 mutant exhibits much slower 13 C incorporation into tocopherols, fumarate, and other tricarboxylic acid (TCA) cycle intermediates than WT and the tat2 mutant. These results indicate that TAT1 and TAT2 function together in tocopherol biosynthesis, with TAT2 having a lesser role, and that TAT1 plays the major role in Tyr degradation in planta. Our study also highlights the importance of Tyr degradation under carbon starvation conditions during dark-induced senescence in plants.

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Aromatic amino acid aminotransferases in plants

Cited by 30 publications

References 198 publications

Imbalance of tyrosine by modulating TyrA arogenate dehydrogenases impacts growth and development of Arabidopsis thaliana

Imbalance of tyrosine by modulating TyrA arogenate dehydrogenases impacts growth and development of Arabidopsis thaliana

General and specialized tyrosine metabolism pathways in plants

TAT1 and TAT2 tyrosine aminotransferases have both distinct and shared functions in tyrosine metabolism and degradation in Arabidopsis thaliana

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