Occurrence, Biosynthesis and Metabolism of Theanine (γ-Glutamyl-L-ethylamide) in Plants: A Comprehensive Review

@article{Ashihara2015OccurrenceBA,
  title={Occurrence, Biosynthesis and Metabolism of Theanine ($\gamma$-Glutamyl-L-ethylamide) in Plants: A Comprehensive Review},
  author={Hiroshi Ashihara},
  journal={Natural Product Communications},
  year={2015},
  volume={10}
}
  • H. Ashihara
  • Published 1 May 2015
  • Environmental Science
  • Natural Product Communications
Theanine (γ-glutamyl-L-ethylamide) is the most abundant non-protein amino acid in tea leaves. In addition to Camellia sinensis, theanine occurs in several plants belonging to the Ericales. Biosynthesis of theanine from glutamic acid and ethylamine by theanine synthetase is present in all organs of tea seedlings, but roots are the major site of theanine biosynthesis in adult tea trees. Theanine is transported from roots to young leaves via the xylem sap. Theanine is hydrolysed to glutamic acid… 
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The results indicated that caffeine and its biosynthetic activity occur only in leaves and stems, while theanine is distributed in all organs, including roots.
Studies on the Biochemical Formation Pathway of the Amino Acid l-Theanine in Tea (Camellia sinensis) and Other Plants.
TLDR
This work compares l-theanine contents between C. sinensis and other plant species and uses a stable isotope labeling approach to elucidate its biosynthetic route and quantifies relevant intermediates and metabolites by mass spectrometry.
New advances in genetic engineering for l-theanine biosynthesis
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TLDR
New insights are provided into the molecular basis for the biosynthesis of theanine, which may facilitate the breeding of high-theanine tea plants for improving the nutritional benefit of tea.
Identification of a Novel Gene Encoding the Specialized Alanine Decarboxylase in Tea (Camellia sinensis) Plants
TLDR
The results suggest that transcription levels of CsAlaDC in root tissues are significantly higher than those in leaf tissues, which may explain why theanine biosynthesis preferentially occurs in the roots of tea plants.
Identification and characterization of cationic amino acid transporters (CATs) in tea plant (Camellia sinensis)
TLDR
The results indicated that the CsCATs expression is regulated by amino acid contents and is sensitive to abiotic stresses, shedding light on the mechanism of amino acid transport in tea plants.
Theanine transporters identified in tea plants (Camellia sinensis L.).
TLDR
The hypothesis that members of the CsAAP family transport theanine and participate in its root-to-shoot delivery in the tea plant is supported.
Biochemical characterization of specific Alanine Decarboxylase (AlaDC) and its ancestral enzyme Serine Decarboxylase (SDC) in tea plants (Camellia sinensis)
TLDR
Comparing to CsAlaDC, its ancestral enzyme CsSDC exhibited a higher specific activity and a better thermal and pH stability, indicating that Cs SDC acquired the optimized function after a longer evolutionary period.
Theanine Improves Salt Stress Tolerance via Modulating Redox Homeostasis in Tea Plants (Camellia sinensis L.)
TLDR
It is suggested that salt stress induces theanine biosynthesize in tea plants to enhance the salt stress tolerance through a CAT-dependent redox homeostasis pathway and genetic evidence supported that catalase-mediated antioxidant scavenging pathway is required.
Gibberellin Increases the Bud Yield and Theanine Accumulation in Camellia sinensis (L.) Kuntze
TLDR
GA3 treatment suggested that GA3 reduced photosynthesis in the tender tea leaves, indicating that the decline of carbon assimilation in tea plants was conducive to the nitrogen metabolism, and it was beneficial to the accumulation of theanine.
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