Characterization of L-phenylalanine metabolism to acetophenone and 1-phenylethanol in the flowers of Camellia sinensis using stable isotope labeling.
Acetophenone (AP) and 1-phenylethanol (1PE) are the two major endogenous volatile compounds in flowers of Camellia sinensis var. Yabukita. Until now no information has been available on the biosynthesis of AP and 1PE in plants. Here we propose that AP and 1PE are derived from L-phenylalanine (L-Phe), based on feeding experiments using stable isotope-labeled precursors L-[(2)H(8)]Phe and L-[(13)C(9)]Phe. The subacid conditions in the flowers result in more hydrogenation than dehydrogenation in the transformation between AP and 1PE. Due to the action of some enzyme(s) responsible for the formation of (R)-1PE from AP in the flowers, (R)-1PE is the dominant endogenous steroisomer of 1PE. The modification of 1PE into nonvolatile glycosidic forms is one of the reasons for why only a little 1PE is released from the flowers. The levels of AP, 1PE, and glycosides of 1PE increase during floral development, whereas the level of L-Phe decreases. These metabolites occur mostly in the anthers.
Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
Fang
F
Dong
Ziyin
Z
Yang
Susanne
S
Baldermann
Yutaka
Y
Kajitani
Shogo
S
Ota
Hisae
H
Kasuga
Yumi
Y
Imazeki
Toshiyuki
T
Ohnishi
Naoharu
N
Watanabe
D000098:Acetophenones / Q000378:metabolism*; D028241:Camellia sinensis / Q000254:growth & development / Q000378:metabolism*; D035264:Flowers / Q000254:growth & development / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods*; D007564:Japan; D010649:Phenylalanine / Q000096:biosynthesis / Q000378:metabolism*; D010626:Phenylethyl Alcohol / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D013662:Tea / Q000737:chemistry; D055549:Volatile Organic Compounds / Q000378:metabolism
D000098:Acetophenones; D010937:Plant Growth Regulators; D013662:Tea; D055549:Volatile Organic Compounds; D010649:Phenylalanine; D010626:Phenylethyl Alcohol; C038699:acetophenone