| | 1 | Author
| G. Kleinehollenhorst, H. Behrens, G. Pegels, N. Srunk, R. W. Ierm Ann | Requires cookie* | | | Title
| Formation of Flavonol 3-O-Diglycosides and Flavonol 3-O-Trigly- cosides by Enzyme Extracts from Anthers of Tulipa cv. Apeldoorn Characterization and Activity o f Three D ifferent O -Glycosyltransferases during Anther Development  | | | | Abstract
| Three distinct glycosyltransferases have been isolated and partially purified from anthers o f Tulipa cv. Apeldoorn. The following designations are proposed; UDP-glucose: flavonol 3-O-glu-cosyltransferase (GT-I), UDP-rhamnose: flavonol 3-O-glucoside rhamnosyltransferase (GT-II) and UDP-xylose: flavonol 3-glycoside xylosyltransferase (GT-III). The three enzymes exhibited an identical pH optimum within the range o f 8.5 —9.0. The estimated molecular weight of GT-I and GT-II was about 40 000, GT-III showed a molecular weight o f 30 000. GT-III required ions like NH^or Ca2+ whereas these ions have almost no influence on GT-I and GT-II activity. The en zymes have a slight requirement for SH-reagents, particularly DTE. As opposed to GT-II activity of GT-I and GT-III is significantly influenced by SH reagents and PCMB. Sucrose enhanced GT-III activity but only slightly GT-I activity, GT-II activity is not influenced. Flavonol aglycones can function as glycosyl acceptor for the GT-I, whereas flavonol 3-O-gly-cosides, luteolin, dihydroquercetin, naringenin, cyanidin, /»-coumaric acid and some other phenols were inactive as acceptor. The best acceptors were isorhamnetin and quercetin (Km: 0.9x10~6 m). GT-II did not accept aglycones as substrates. For this enzyme flavonol 3-O-glu-cosides were the most attractive substrates. GT-III did not have any affinity towards aglycones, too. This enzyme exhibited a high specificity for flavonol 3-O-glucosides as well as flavonol 3-0-galactosides. Both enzymes, the GT-II and GT-III, were able to glycosylate flavonol 3-O-digly-cosides forming triglycosides. UDP-glucose (K m= l.OxlO-4 m), UDP-rhamnose and UDP-xylose where shown to be the best glycosyl donors for GT-I, GT-II or GT-III respectively. The glycosyl transfer catalysed by the GT-I was shown to be a freely reversible reaction. In the whole anthers, highest specific activities o f GT-I and GT-II were found during late stages of anther development. Similar results were obtained using the contents o f anthers or the tapetum fraction. In contrary, high GT-III activity can be detected already in young stages o f anther devel opment. The highest activities o f the three glycosyltransferases were found in the tapetum frac tion, whereas the pollen fraction exhibited only poor activities. | | | |
Reference
| Z. Naturforsch. 37c, 587—599 (1982); received March 18 1982 | | | |
Published
| 1982 | | | |
Keywords
| Liliaceae, Tulipa cv Apeldoorn, Anthers, Flavonoid Metabolism, Enzymatic, O-Glycosyltransferase | | | |
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| default:Reihe_C/37/ZNC-1982-37c-0587.pdf | | | | Identifier
| ZNC-1982-37c-0587 | | | | Volume
| 37 | |
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