Characterization of Coumarin-Specific Prenyltransferase Activities inCitrus limonPeel

Abstract

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.

Molecular Cloning and Characterization of a Geranyl Diphosphate-Specific Aromatic Prenyltransferase from Lemon

“…We found that the native U8GT activity of lemon flavedo was 12% of the activity of bergaptol 5-O-geranyltransferase activity, which yields bergamottin, the main coumarin derivative in the lemon flavedo (Munakata et al, 2012). In contrast to its high native enzymatic activity in lemon flavedo, the endogenous level of 8GU in these lemon organs was very low, suggesting that 8GU serves as an intermediate that is converted to other unidentified metabolites, which accumulate, along with other coumarin components, in the oil glands of citrus flavedo (Frérot and Decorzant, 2004).…”

“…For example, umbelliferone-dimethylallyltransferase activities were reported in cultured parsley (Petroselinum crispum) cells, Ruta graveolens, and Ammi majus, and plastidial localization of the enzyme activity is also reported (Ellis and Brown, 1974;Dhillon and Brown, 1976;Tietjen and Matern, 1983;Hamerski and Matern, 1988;Hamerski et al, 1990). In addition, bergaptol 5-Ogeranyltransferase activity, which yields bergamottin, a major coumarin derivative, was characterized using the microsomal fraction of lemon (Citrus limon) peel flavedo, the outer part of the lemon fruit (Frérot and Decorzant, 2004;Munakata et al, 2012). In the lemon flavedo, 8-geranyltransferase activity for umbelliferone was also detected (Munakata et al, 2012).…”

“…In addition, bergaptol 5-Ogeranyltransferase activity, which yields bergamottin, a major coumarin derivative, was characterized using the microsomal fraction of lemon (Citrus limon) peel flavedo, the outer part of the lemon fruit (Frérot and Decorzant, 2004;Munakata et al, 2012). In the lemon flavedo, 8-geranyltransferase activity for umbelliferone was also detected (Munakata et al, 2012). To date, only one gene encoding these enzymes has been described; this gene, which encodes a parsley PT (PcPT), was very recently isolated (Karamat et al, 2014).…”

Chemical Characterization of 64 Propolis Samples from Hakkari, Turkey

“…Coumarins, which are a wide class of flavonoids, play an important role in the defense mechanism of plants and have many useful biological effects on human health [34]. In this study, coumarins were determined in M3, M4, M7, M11, M13, Y2,Y3, Y4, Y5, Y7, Y9, Y13, Y14, Y16, Y17, Y19, S10, S12, S20, S21, S22, S23, S24, S25, S26, S27, S28, and S29 samples (Table 3).…”

Oxyprenylated ferulic acid derivatives in Italian citrus liqueurs

“…It is noteworthy to underline that in pure lemon, orange and mandarin juices, analysed under the same experimental conditions as above, GOFA and BPA acid having not been detected. This result may be explained by the recent discovery that the prenylation of phenylpropanoid cores is a biosynthetic enzymatic activity typically located in Citrus skins (Munakata et al 2012). The occurrence of oxyprenylated secondary metabolites related to GOFA and BPA, namely farnesyloxy-and/or geranylgeranyloxy-derivatives, cannot be excluded, although there are no citations in the literature about the presence of such natural products in the genus Citrus (Epifano et al 2013).…”