Amino acids give tea its brothiness, or umami taste. Tea leaves contain 15.5 per cent protein in dry weight basis and 4.5 per cent free amino acids. Among the amino acids found in young tea leaves are aspartic acid, glutamic acid, glycine, serine, glutamine, tyrosine, threonine, α-alanine, β-alanine, valine, leucine, iso-leucine, phenylealanine, lysine, arginine, histidin, tryptophan, asparigin, prolin, and theanine. Theanine and glutamic acid are the major amino acids present in tea. Out of these, the most abundant of which is theanine. You will be thrilled to know that Camellia sinensis (tea plant), Boletus badius (a mushroom) and a plant called guayusa are the only three natural sources of theanine found so far in nature.
The amino acids are one of the major components that give green tea its specific taste and antagonistic in action to caffeine.