Dem IPB wird erneut ein beispielhaftes Handeln im Sinne einer chancengleichheitsorientierten Personal- und Organisationspolitik bescheinigt. Das Institut erhält zum 6. Mal in Folge das TOTAL E-QUALITY…
Die Plant Science Student Conference (PSSC) wird seit 20 Jahren im jährlichen Wechsel von Studierenden der beiden Leibniz-Institute IPK und IPB organisiert. Im Interview erläutern Christina Wäsch…
Samappito, S.; Page, J. E.; Schmidt, J.; De-Eknamkul, W.; Kutchan, T. M.;Aromatic and pyrone polyketides synthesized by a stilbene synthase from Rheum tataricumPhytochemistry62313-323(2003)DOI: 10.1016/S0031-9422(02)00545-9
A cDNA encoding a stilbene synthase, RtSTS, was isolated from the rhizomes of Tatar rhubarb, Rheum tataricum L. (Polygonaceae), a medicinal plant containing stilbenes and other polyketides. Recombinant RtSTS was expressed in E. coli and assayed with acetyl-coenzyme A (CoA), n-butyryl-CoA, isovaleryl-CoA, n-hexanoyl-CoA, cinnamoyl-CoA and p-coumaroyl-CoA as primers of polyketide synthesis. RtSTS synthesized resveratrol and a trace amount of naringenin chalcone from p-coumaroyl-CoA, supporting the enzyme's identification as a resveratrol-type stilbene synthase (EC 2.3.1.95). Bis-noryangonin and p-coumaroyl triacetic acid lactone (CTAL)-type pyrones were observed in minor amounts in the reaction with p-coumaroyl-CoA and as major products with cinnamoyl CoA. As well, such pyrones, and not aromatic polyketides, were identified as the only products in assays with aliphatic and benzoyl CoA esters. Acetonyl-4-hydroxy-2-pyrone, a pyrone synthesized from acetyl-CoA, was identified as a new product of a stilbene synthase. Using Northern blot analysis, RtSTS transcript was found to be highly expressed in R. tataricum rhizomes, with low transcript levels also present in young leaves. This expression pattern correlated with the occurrence of resveratrol, which was detected in higher amounts in R. tataricum rhizomes compared with leaves and petioles using HPLC. Few stilbene synthases have been found in plants, and the identification of RtSTS provides additional sequence and catalytic information with which to study the evolution of plant polyketide synthases.A cDNA encoding a plant polyketide synthase was isolated from Rheum tataricum and functionally charactarized as a resveratrol-forming stilbene synthase.
Publikation
Richter, W. G.; Cappi, M. W.; Henkel, B.; Hess, S.; Surivet, J. P.; Baeschlin, D.; Hubschwerlen, C.; Höfle, G.; Wessjohann, L. A.; Eichelberger, U.;Second generation epothilones and their biological propertiesClin. Cancer Res.96137(2003)
Raith, K.; Neubert, R.; Poeaknapo, C.; Boettcher, C.; Zenk, M. H.; Schmidt, J.;Electrospray tandem mass spectrometric investigations of morphinansJ. Am. Soc. Mass Spectrom.141262-1269(2003)DOI: 10.1016/S1044-0305(03)00539-7
In this study positive ESI tandem mass spectra of the [M+H]+ ions of morphinan alkaloids obtained using an ion trap MS were compared with those from a triple quadrupole MS. This allows to assess the differences of the tandem-in-time versus the tandem-in-space principle, often hampering the development of ESI MS/MS libraries. Fragmentation pathways and possible fragment ion structures were discussed. In order to obtain elemental composition, accurate mass measurements were performed. According to the MS/MS fragmentation pathway, the investigated compounds can be grouped into 4 subsets: (1) morphine and codeine, (2) morphinone, codeinone, and neopinone, (3) thebaine and oripavine, (4) salutaridine and salutaridinol. Salutaridinol-7-O-acetate shows a different fragmentation behavior because of the favored loss of acetic acid. Although most fragment ions occur in both ion trap and triple quad tandem mass spectra, some are exclusively seen in either type. For triple quad, quadrupole time-of-flight and FT-ICR MS/MS, the base peak of morphine results from an ion at m/z 165 that contains neither nitrogen nor oxygen. This ion is not found in ion trap MS/MS, but in subsequential MS3 and MS4.