Identification of Key Post-modification Enzymes Involved in the Biosynthesis of Lanostane-type Triterpenoids in the Medicinal Mushroom Antrodia camphorata.

Abstract

Lanostane-type triterpenoids are important bioactive secondary metabolites of mushrooms, though their biosynthetic study has been challenging due to scattered genes. Herein, the strategies of combining metabolomics and transcriptomics analyses, functional motif blast, and KEGG (Kyoto Encyclopedia of Genes and Genomes) annotation were used to discover three key post-modification enzymes involved in the biosynthesis of lanostanoids in the medicinal mushroom Antrodia camphorata. The cytochrome P450 enzyme AcCYP4 could generate a Δ^7,9(11) diene structure and introduce a 15α-hydroxy group to the triterpene skeleton. The short-chain dehydrogenase AcSDR6 could regio- and stereo- selectively catalyze the dehydrogenation of 3β-OH to produce 3-keto triterpenoids, and the catalytic mechanisms were interpreted by crystal structure analysis. AcSMT1 could introduce the methyl group at C-24 to produce a unique 31-carbon triterpene skeleton. This work elucidated the major biosynthetic pathway of Antrodia lanostanoids in vitro, and the discovered enzymes could be used to synthesize a series of bioactive triterpenoids.