Abstract
Covering: up to September 2015. Meroterpenoids are hybrid natural products that partially originate from the terpenoid pathway. The meroterpenoids derived from fungi display quite diverse structures, with a wide range of biological properties. This review summarizes the molecular bases for their biosyntheses, which were recently elucidated with modern techniques, and also discusses the plausible biosynthetic pathways of other related natural products lacking genetic information. (Complementary to the coverage of literature by Geris and Simpson in Nat. Prod. Rep., 2009, 26, 1063-1094.).
Highlights
The tetracyclic core of is generated collaboratively by the NR-polyketide synthase (PKS) VrtA, the Claisen cyclase VrtG, and the FMO VrtH, from one molecule of malonamoyl-coenzyme A (CoA) and nine molecules of malonylCoA, yielding 208.142 The P450 VrtE and the methyltransferase VrtF convert into 209, which is further geranylated by the dimethylallyltryptophan synthases (DMATSs)-type PTase VrtC to generate 210.143 The very last step of the biosynthesis involves the cyclization of the geranyl moiety, and interestingly this process is catalyzed by the P450 VrtK and not by the canonical terpene cyclases (TPCs)
Considering the structures of 211 and 212, it was thought that the terpenoid motif of these compounds is derived from geranyl pyrophosphate (GPP), but interestingly, a biochemical experiment has revealed that PenI, which is the PTase that accepts 217 as a substrate, only produces the dimethylallylated molecule 218.146 In the step, the FMO PenH catalyzes dehydrogenation to generate the conjugated diene 219, and the introduced exo-methylene hereby serves as a nucleophile required for the second prenylation by the DMATS-like PTase PenG
This review has summarized recent biosynthetic studies of fungal meroterpenoids at the genetic/enzymatic levels
Summary
Meroterpenoids are hybrid natural products partially derived from terpenoid pathways as the pre x “mero-” means “part, partial, and fragment”.1 On the basis of their de nition, numerous compounds derived from animals, plants, bacteria, and fungi can be grouped into this class of natural products, which range from widely distributed molecules to speciesspeci c secondary metabolites. Compound 13 serves as a biosynthetic intermediate of lolitrem B [14], which is produced by Neotyphodium lolii and is a potent tremorgenic neurotoxin.19 A er a short period of experience in industry, he moved back to The University of Tokyo as a project researcher, and was appointed as an assistant professor at the same university (2013–2015) He obtained his Ph.D. in pharmaceutical sciences from The University of Tokyo in 2015. This review is intended to continue the coverage of the literature previously reviewed in this journal by Geris and Simpson.1 It will mainly focus on the recent biosynthetic studies of fungal meroterpenoids for which the biosynthetic genes/enzymes have been elucidated, and discuss the plausible biosynthetic mechanisms of some related meroterpenoids for which genetic information is lacking. Fungal meroterpenoids are quite o en generated via the addition of a C5 isoprene unit, catalyzed by dimethylallyltryptophan synthases (DMATSs), but we will limit this review to the meroterpenoids originating from relatively long prenyl chains (more than C5) as the functions of DMATSs have been well summarized elsewhere.
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