Bifunctional Sesquiterpene/Diterpene Synthase Agr2 from Cyclocybe aegerita Gives Rise to the Novel Diterpene Cyclocybene

Summary

Scientists discovered that a fungal enzyme from the black poplar mushroom (Cyclocybe aegerita) can produce two different types of beneficial compounds called terpenes. Using a baker’s yeast relative as a host organism, they found that the enzyme makes both a known sesquiterpene and an entirely new diterpene compound they named cyclocybene. This discovery shows that fungi can be better factories for producing these valuable compounds than bacteria previously used, opening doors for developing new medicines, fragrances, and biofuels.

Background

Cyclocybe aegerita is a model mushroom known for its diverse terpenome containing various volatile and nonvolatile terpenes. The terpene synthase Agr2 was previously identified as producing only the sesquiterpene viridiflorene when expressed in E. coli, but its genomic location near a putative GGPP synthase suggested additional diterpene production capacity.

Objective

To determine whether the terpene synthase Agr2 from Cyclocybe aegerita possesses bifunctional activity by heterologously expressing it in Coprinopsis cinerea and characterizing all products produced.

Results

Heterologous expression of Agr2 in C. cinerea revealed two terpene products: the known sesquiterpene viridiflorene and a previously unknown diterpene identified as cyclocybene with molecular formula C20H32. Substrate biotransformation experiments confirmed that Agr2 can utilize both FPP and GGPP as substrates. Cyclocybene production reached approximately 1.9 mg/L in culture supernatant by day 16.

Conclusion

Agr2 is a bifunctional terpene synthase capable of producing both sesqui- and diterpenes, with C. cinerea demonstrating superior suitability as an expression host for fungal diterpenes compared to E. coli due to its superior isoprenoid precursor availability.
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