Journal
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 69, Issue 50, Pages 15354-15361Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jafc.1c06660
Keywords
L-alanine; amino acid; Camellia sinensis; ethylamine; L-glutamate; L-theanine
Funding
- National Natural Science Foundation of China [31922077]
- Regional Key Project of Science and Technology Service Network Plan of the Chinese Academy of Sciences [KFJ-STS-QYZX-093]
- Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams [2021KJ120]
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In tea plants, L-alanine is mainly located in vacuoles and mitochondria of root cells, while ethylamine is mainly found in the cortex with epidermis. Research discovered that in tea plants, L-alanine is converted to L-theanine via L-glutamate instead of ethylamine.
Tea plants (Camellia sinensis) specifically produce L-theanine, which contributes to tea function and taste. Ethylamine is a limiting factor differentiating L-theanine accumulation between tea and other plants. Ethylamine has long been assumed to be derived from L-alanine in tea. In this study, the L-alanine content in tea root cells was mainly located in vacuoles and mitochondria using a nonaqueous fractionation technique, while alanine decarboxylase in tea (CsADC) was located in the cytoplasm. Although CsADC was able to catalyze L-alanine decarboxylation to produce ethylamine in vitro, it may not provide the same enzyme activity in tea plants. Stable isotope-labeled precursor tracing in tea plants discovered that L-alanine is not a direct precursor of ethylamine but a precursor of L-glutamate, which is involved in L-theanine biosynthesis in tea. Cortex with epidermis from root tissue was the main location of ethylamine. In summary, L-alanine is converted to L-theanine via L-glutamate not ethylamine in tea plants in vivo.
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