Journal
PLANT SCIENCE
Volume 211, Issue -, Pages 61-69Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.plantsci.2013.07.003
Keywords
Amaranthus tricolor L; Betanidin glucosyltransferase; Flavonoids; Liquid chromatography-mass spectrometry; Peptide mass fingerprinting
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Funding
- Department of Biotechnology, Government of India [BT/PR8750/NDB/52/19/2007]
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Betacyanins are the major pigments present in Amaranthus tricolor, a leafy vegetable consumed globally. The terminal glycosyltaion of the aglycone betanidin is an important step in the biosynthesis of this natural red antioxidant pigment. A betanidin 5-O-glucosyltransferase (BGT) was fully purified to 134 folds (specific activity, 265.2 nkat mg(-1)) from the red amaranth by ammonium sulfate precipitation followed by hydrophobic interaction, anion exchange and size exclusion chromatography. Homogeneity of the purified protein was confirmed by 2-dimensional polyacrylamide gel electrophoresis (2D PAGE). The molecular weight of the enzyme determined by liquid chromatography-mass spectrometry (LC-MS) was found to be 62.8 kDa. Furthermore, the enzyme glycosylated flavonoids (kaempferol and quercetin) but not anthocyanidins, presence of which is mutually exclusive to betacyanin accumulating plants. The apparent K-m (344 +/- 234 mu M) and V-max (17.24 mu M min(-1)) of the enzyme were determined by LC-MS/MS. Peptide mass fingerprinting of the purified protein showed 38.4% coverage of peptide masses with anthocyanidin 3-O-glucosyltransferase from Zea mays. Study on this purified enzyme, for the first time, revealed its role of glycosylation in biosynthesis of betacyanin in A. tricolor and indicates promiscuous substrate-specificity. (c) 2013 Elsevier Ireland Ltd. All rights reserved.
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