Cloning and characterization of a glucosyltransferase that reacts on 7-hydroxyl group of flavonol and 3-hydroxyl group of coumarin from tobacco cells.
In higher plants, secondary metabolites are often converted to their glycoconjugates by glycosyltransferases (GTases). We cloned a cDNA encoding GTase (NtGT2) from tobacco (Nicotiana tabacum L.). The recombinant enzyme expressed in Escherichia coli (rNTGT2) showed glucosylation activity against several kinds of phenolic compounds, particularly the 7-hydroxyl group of flavonoids and 3-hydroxycoumarin. The K(m) values of kaempferol and 3-hydroxycoumarin with rNTGT2 are 6.5 microM and 23.6 microM, respectively. The deduced amino acid sequence of NTGT2 shows 60-70% identity to that of anthocyanin 5-O-glucosyltransferase (A5GT); rNTGT2 did not show activity against the anthocyanins tested. NtGT2 gene expression was induced by treating tobacco cells with plant hormones such as salicylic acid. We consider that NtGT2 gene might have evolved from the same ancestral gene as the A5GT genes to the stress-inducible GTases that react on several phenolic compounds.
Taguchi
Goro
G
Division of Gene Research, Research Center for Human and Environmental Sciences, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan. gtagtag@giptc.shinshu-u.ac.jp
Ubukata
Takahisa
T
Hayashida
Nobuaki
N
Yamamoto
Hirobumi
H
Okazaki
Mitsuo
M
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003374:Coumarins / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020539:Sequence Analysis, Protein; D014026:Nicotiana / Q000737:chemistry* / Q000378:metabolism*
D003374:Coumarins; D005419:Flavonoids; D010937:Plant Growth Regulators; D011994:Recombinant Proteins; D017665:Hydroxyl Radical; C030123:coumarin; C036655:1,3-alpha-D-glucan synthase; D005964:Glucosyltransferases