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'O Methyltransferase' in keywords
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1985 (1)
1983 (1)
1979 (1)
1Author    Kim Thresh, RagaiK. IbrahimRequires cookie*
 Title    Are Spinach Chloroplasts Involved in Flavonoid O-Methylation?  
 Abstract    Intact spinach chloroplasts, which were isolated on a cushion of Percoll and purified on discon­ tinuous sucrose gradients, were found to adsorb appreciable amounts of high specific activity, cytosolic O-methyltransferases. The latter activity was readily eliminated after washing the chloroplast pellet with 0.1 m phosphate in sucrose gradient buffer and finally with 0 .1% nonidet. Furthermore, the OMT activity of spinach leaves was resolved by chromatography on DEAE-Sepharose CL-6B into caffeic acid (COMT) and flavonoid (FOMT) O-methyltransferase ac­ tivities, and purified to 30-and 50-fold, respectively. The similarities between the FOMT/COMT activity ratios and the methylation patterns of intact chloroplasts and their supernatants, as well as those of purified leaf preparations, suggest non-specific binding of cytosolic OMTs to chloroplast envelopes. It is concluded, therefore, that spinach chloroplasts are not involved in the methylation of phenylpropanoid or flavonoid compounds. These results call attention for the re-evaluation of the role of this organelle in the biosynthesis or accumulation of plant secondary metabolites. 
  Reference    Z. Naturforsch. 40c, 331 (1985); received December 11 1984/February 26 1985 
  Published    1985 
  Keywords    Spinacea oleracea, Chenopodiaceae, Chloroplasts, O-Methyltransferase, Caffeic Acid, Quercetin 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0331.pdf 
 Identifier    ZNC-1985-40c-0331 
 Volume    40 
2Author    Yun-Fuk Tsang, RagaiK. IbrahimRequires cookie*
 Title    Evidence for the Existence of meta and para Directing O-Methyltransferases in Tobacco Cell Cultures  
 Abstract    The O-methyltransferase of tobacco cell culture was resolved to its meta and para directing forms by chromatography on DEAE-cellulose. Despite similarities in molecular weights and pi values of the two forms, however, evidence from pH optima, SH-group inhibitors, methylation ratios, SDS-acrylamide gels and mixed substrate experiments indicates the existence of two discrete enzymes acting at the meta and para positions of caffeic acid and quercetin, respectively; though the latter enzyme was less substrate specific than its meta counterpart. 
  Reference    Z. Naturforsch. 34c, 46 (1979); received November 17 1978 
  Published    1979 
  Keywords    O-Methyltransferase, Enzyme, meta and para Methylation, Phenols, Tobacco Cell Suspension Culture, Nicotiana tabcaum 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0046.pdf 
 Identifier    ZNC-1979-34c-0046 
 Volume    34 
3Author    Maurice Jay, Vincenzo De Luca, Ragai IbrahimRequires cookie*
 Title    Meta-Methylation o f Flavonol Rings A (8-) and B (3'-) Is Catalysed by Two Distinct O-Methyltransferases in Lotus corniculatus  
 Abstract    Two O-methyltransferases specific for flavonol rings A and B were isolated from young flower buds of Lotus corniculatus. They were partially purified by ammonium sulphate precipitation and successive chromatography on Sephadex G-100 and Polybuffer ion exchanger. One enzyme focused at pi 5.5 and catalysed the O-methylation of position 8 of flavonols with a pH optimum of 8.1. The other enzyme had a pi o f 5.1 and preferentially attacked position 3' at an optimum pH of 7.7. The methylated products o f both enzymes seem to contribute to the flower colour of Lotus and may be used as biochemical markers in genetic studies of this genus. 
  Reference    Z. Naturforsch. 38c, 413 (1983); received December 21 1982 
  Published    1983 
  Keywords    Lotus corniculatus, Leguminosae, O-Methyltransferase, Flavonols, 8-O-Methylation, 3'-0-Methylation 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0413.pdf 
 Identifier    ZNC-1983-38c-0413 
 Volume    38