The dual fate of L-theanine in tea: Metabolic regulation and processing transformations

L-Theanine, the signature non-protein amino acid unique to tea (Camellia sinensis), is crucial for tea's health benefits and umami taste, yet its biosynthesis and stability face increasing threats from climate change and processing challenges.

This review intends to provide the comprehensive synthesis of L-theanine's dual fate from biosynthesis to cup by integrating recent breakthroughs in its biosynthesis, transport, stress responses, and processing transformations.

This review systematically elucidated the complete "root-to-shoot" metabolic pathway regulated by key genes and transporters of L-theanine, and summarized stress-adaptive mechanisms where L-theanine serves as both nitrogen reservoir and stress protectant, and further constructed a comprehensive analytical for L-theanine-derived flavor compound formation during tea processing. By bridging fundamental discoveries in plant physiology with practical applications in food chemistry, this work provides new insights into innovative strategies for developing climate-resilient tea varieties through molecular breeding and optimizing processing technologies to enhance product quality.