An uncharacterized terpene cyclase from Streptomyces pratensis was identified as (+)-(1(10)E,4E,6S,7R)-germacradien-6-ol synthase. The enzyme product exists as two interconvertible conformers, resulting in complex NMR spectra. For the complete assignment of NMR data, all fifteen ((13)C1)FPP isotopomers (FPP=farnesyl diphosphate) and ((13)C15)FPP were synthesized and enzymatically converted. The products were analyzed using various NMR techniques, including (13)C, (13)C COSY experiments. The ((13)C)FPP isotopomers were also used to investigate the thermal rearrangement and EI fragmentation of the enzyme product.

Complex cyclization reactions of fungal meroterpenoid cyclases.

The volatiles released by agar plate cultures of nineteen actinomycetes whose genomes were recently sequenced were collected by use of a closed-loop stripping apparatus (CLSA) and analysed by GC/MS. In total, 178 compounds from various classes were identified. The most interesting findings were the detection of the insect pheromone frontalin in Streptomyces varsoviensis, and the emission of the unusual plant metabolite 1-nitro-2-phenylethane. Its biosynthesis from phenylalanine was investigated in isotopic labelling experiments. Furthermore, the identified terpenes were correlated to the information about terpene cyclase homologs encoded in the investigated strains. The analytical data were in line with functionally characterised bacterial terpene cyclases and particularly corroborated the recently suggested function of a terpene cyclase from Streptomyces violaceusniger by the identification of a functional homolog in Streptomyces rapamycinicus.

Eine uncharakterisierte Terpenzyklase aus Streptomyces pratensis wurde als (+)‐(1(10)E,4E,6S,7R)‐Germacradien‐6‐ol‐Synthase identifiziert, deren Produkt als zwei ineinander konvertierbare Konformere existiert, wodurch komplexe NMR‐Spektren resultieren. Für eine komplette Zuordnung der NMR‐Daten wurden alle fünfzehn Isotopomere des (13C1)FPP sowie (13C15)FPP synthetisiert und enzymatisch umgesetzt und die Produkte durch diverse NMR‐Methoden einschließlich 13C,13C‐COSY analysiert. Die (13C)FPP‐Isotopomere wurden weiterhin für die Untersuchung der thermischen Umlagerung und des EI‐Fragmentierungsmechanismus des Enzymprodukts verwendet.

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