Characterization of coumarin-specific prenyltransferase activities in Citrus limon peel.
Coumarins, a large group of polyphenols, play important roles in the defense mechanisms of plants, and they also exhibit various biological activities beneficial to human health, often enhanced by prenylation. Despite the high abundance of prenylated coumarins in citrus fruits, there has been no report on coumarin-specific prenyltransferase activity in citrus. In this study, we detected both O- and C-prenyltransferase activities of coumarin substrates in a microsome fraction prepared from lemon (Citrus limon) peel, where large amounts of prenylated coumarins accumulate. Bergaptol was the most preferred substrate out of various coumarin derivatives tested, and geranyl diphosphate (GPP) was accepted exclusively as prenyl donor substrate. Further enzymatic characterization of bergaptol 5-O-geranyltransferase activity revealed its unique properties: apparent K(m) values for GPP (9 µM) and bergaptol (140 µM) and a broad divalent cation requirement. These findings provide information towards the discovery of a yet unidentified coumarin-specific prenyltransferase gene.
Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Japan.
Ryosuke
R
Munakata
Tsuyoshi
T
Inoue
Takao
T
Koeduka
Kanako
K
Sasaki
Yusuke
Y
Tsurumaru
Akifumi
A
Sugiyama
Yoshihiro
Y
Uto
Hitoshi
H
Hori
Jun-Ichi
J
Azuma
Kazufumi
K
Yazaki
D002413:Cations, Divalent / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002957:Citrus / Q000737:chemistry / Q000201:enzymology*; D003374:Coumarins / Q000737:chemistry / Q000378:metabolism*; D004122:Dimethylallyltranstransferase / Q000302:isolation & purification* / Q000378:metabolism; D011756:Diphosphates / Q000737:chemistry / Q000378:metabolism; D004224:Diterpenes / Q000737:chemistry / Q000378:metabolism; D011564:Furocoumarins / Q000737:chemistry / Q000378:metabolism*; D051228:Geranyltranstransferase / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000737:chemistry / Q000201:enzymology; D010940:Plant Proteins / Q000302:isolation & purification* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
D002413:Cations, Divalent; D003374:Coumarins; D011756:Diphosphates; D004224:Diterpenes; D011564:Furocoumarins; D010940:Plant Proteins; C511282:geranyl diphosphate; D004122:Dimethylallyltranstransferase; D051228:Geranyltranstransferase; C080771:bergaptol