TAILIEUCHUNG - Báo cáo khóa học: Furanocoumarin biosynthesis in Ammi majus L. Cloning of bergaptol O-methyltransferase

Plants belonging to the Apiaceae or Rutaceae accumulate methoxylated psoralens, such as bergapten or xanthotoxin, as the final products of their furanocoumarin biosynthesis, and the rate of accumulationdepends on environmental and other cues. DistinctO-methyltransferase activities had been reported to methylate bergaptol to bergapten and xantho-toxol to xanthotoxin, from induced cell cultures of Ruta graveolens,Petroselinum crispumandAmmi majus. Bergap-tol 5-O-methyltransferase (BMT) cDNA was cloned from dark-grownAmmi majusL. cells treatedwith a crude fungal elicitor. . | Eur. J. Biochem. 271 932-940 2004 FEBS 2004 doi Furanocoumarin biosynthesis in Ammi majus L. Cloning of bergaptol ơ-methyltransferase Marc Hehmann1 Richard Lukacin1 Halina Ekiert2 and Ulrich Matern1 1Institut fur Pharmazeutische Biologie Philipps-Universitat Marburg Germany 2Department of Pharmaceutical Botany Collegium Medicum Jagiellonian University Krakow Poland Plants belonging to the Apiaceae or Rutaceae accumulate methoxylated psoralens such as bergapten or xanthotoxin as the final products of their furanocoumarin biosynthesis and the rate of accumulation depends on environmental and other cues. Distinct O-methyltransferase activities had been reported to methylate bergaptol to bergapten and xantho-toxol to xanthotoxin from induced cell cultures of Ruta graveolens Petroselinum crispum and Ammi majus. Bergap-tol 5-O-methyltransferase BMT cDNA was cloned from dark-grown Ammi majus L. cells treated with a crude fungal elicitor. The translated polypeptide of kDa composed of 354 amino acids revealed considerable sequence similarity to heterologous caffeic acid 3-O-methyltransferases COMTs . For homologous comparison COMT was cloned from A. majus plants and shown to share 64 identity and about 79 similarity with the BMT sequence at the polypeptide level. Functional expression of both enzymes in Escherichia coli revealed that the BMT activity in the bacterial extracts was labile and rapidly lost on purification whereas the COMT activity remained stable. Furthermore the recombinant AmBMT which was most active in potassium phosphate buffer of pH 8 at 42 C showed narrow substrate specificity for bergaptol Km SAM M Km Bergaptoi M when assayed with a variety of substrates including xanthotoxol while the AmCOMT accepted 5-hydroxyferulic acid esculetin and other substrates. Dark-grown A. majus cells expressed significant BMT activity which nevertheless increased sevenfold within 8 h upon the addition of elicitor and reached a .

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