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The dihydrochalcone phlorizin (phloretin 2¢-glucoside) contributes to the flavor, color and health benefits of apple fruit and processed products. A genomics approach was used to identify the geneMdPGT1in apple (Ma-lus x domestica) with homology to the UDP-glycosyltransferase 88 family of uridine diphosphate glycosyltransferases that show specificity towards flavonoid substrates. | ễFEBS Journal Isolation and characterization of a novel glycosyltransferase that converts phloretin to phlorizin a potent antioxidant in apple Hélène Jugde1 Danny Nguy1 Isabel Moller1 Janine M. Cooney2 and Ross G. Atkinson1 1 The Horticulture and Food Research Institute of New Zealand Ltd HortResearch Auckland New Zealand 2 The Horticulture and Food Research Institute of New Zealand Ruakura Hamilton New Zealand Keywords antioxidant apple phloretin phlorizin uridine diphosphate glycosyltransferase Correspondence R. Atkinson Mt Albert Research Centre HortResearch Private Bag 92 169 Auckland New Zealand Fax 64 9 925 7001 Tel 64 9 925 7000 E-mail ross.atkinson@hortresearch.co.nz Note Nucleotide sequence data are available in the DDBJ EMBL GenBank databases under the accession number EU246349 Received 27 February 2008 revised 22 May 2008 accepted 28 May 2008 The dihydrochalcone phlorizin phloretin 2 -glucoside contributes to the flavor color and health benefits of apple fruit and processed products. A genomics approach was used to identify the gene MdPGTl in apple Ma-lus x domestica with homology to the UDP-glycosyltransferase 88 family of uridine diphosphate glycosyltransferases that show specificity towards flavonoid substrates. Expressed sequence tags for MdPGTl were found in all tissues known to produce phlorizin including leaf flower and fruit. However the highest expression was measured by quantitative PCR in apple root tissue. The recombinant MdPGT1 enzyme expressed in Escherichia coli glycosylated phloretin in the presence of 3H -UDP-glucose but not other apple antioxidants including quercetin naringenin and cyanidin. The product of phloretin and UDP-glucose co-migrated with an authentic phlorizin standard. LC MS indicated that MdPGT1 could glycosylate phloretin in the presence of three sugar donors UDP-glucose UDP-xylose and UDP-galactose. This is the first report of functional characterization of a UDP-glycosyltransferase that utilizes a dihydrochalcone as its
