Mechanistic characterisation of a sesquiterpene synthase for asterisca-1,6-diene from the liverwort Radula lindenbergiana and implications for pentalenene biosynthesis

Characterization of microbial type terpene synthases from two liverworts Lophocolea bidentata and Nardia scalaris

Microbial terpene synthase-like (MTPSL) enzymes from the two liverworts Nardia scalaris (Gymnomitriaceae) and Lopcholea bidentata (Lophocoleaceae) were characterized in yeast. The hexane extract of the fresh plant material was also analyzed for its terpenoid content. Following the expression of the enzymes in yeast (WAT11), the volatile terpenoid products were analyzed using GC-MS, and their scent was qualitatively evaluated. Four full lengths MTPSLs from L. bidentata and four from N. scalaris were identified in the transcriptome data and expressed in yeast. Three MTPSLs from L. bidentata and two from N. scalaris were found to be biochemically active in yeast, and all of these were found to be sesquiterpene synthases without any monoterpenoid products. These represent the first terpene synthases characterized from these two plants. LbMTPSL1 was found to be a murolene synthase, LbMTPSL3 was a cubenene synthase, and LbMTPSL5 had α-selinene and β-elemene as the major products. For N. scalaris it was found that NsMTPSL3 was a viridiflorol synthase and NsMTPSL4 was a α/β-chamigrene synthase with at least five other minor products. The 3D structure of the enzymes was modelled using CPH-models, in order to enhance the understanding of the biochemical differences of the enzymes. The models clearly show that these MTPSL only contain one α-domain, which is characteristic of MTPSLs and is previously described for similar enzymes. The bioactivities of the enzymes align with compounds identified in the two liverworts, and this study represents the first onset of further investigations into terpenoid biochemistry of Lopcholea and Nardia species.

Mechanistic characterisation of the diterpene synthase for clitopilene and identification of isopentalenene synthase from the fungus Clitopilus passeckerianus

Two terpene synthases from the pleuromutilin producing fungus Clitopilus passeckerianus were functionally characterised. The first enzyme CpTS1 produces the new diterpene clitopilene with a novel 6-6-5-5 tetracyclic skeleton, while the second enzyme CpTS2 makes the new sesquiterpene isopentalenene. The CpTS1 reaction mechanism was studied in depth using experimental and theoretical approaches.

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