Divergent Biosynthesis of Bridged Polycyclic Sesquiterpenoids by a Minimal Fungal Biosynthetic Gene Cluster.

The bridged polycyclic sesquiterpenoids derived from sativene, isosativene, and longifolene have unique structures, and many chemical synthesis approaches with at least 10 steps have been reported. However, their biosynthetic pathway remains undescribed. A minimal biosynthetic gene cluster (BGC), named bip, encoding a sesquiterpene cyclase (BipA) and a cytochrome P450 (BipB) is characterized to produce such complex sesquiterpenoids with multiple carbon skeletons based on enzymatic assays, heterologous expression, and precursor experiments. BipA is demonstrated as a versatile cyclase with (-)-sativene as the dominant product and (-)-isosativene and (-)-longifolene as minor ones. BipB is capable of hydroxylating different enantiomeric sesquiterpenes, such as (-)-longifolene and (+)-longifolene, at C-15 and C-14 in turn. The C-15- or both C-15- and C-14-hydroxylated products are then further oxidized by unclustered oxidases, resulting in a structurally diverse array of sesquiterpenoids. Bioinformatic analysis reveals the BipB homologues as a discrete clade of fungal sesquiterpene P450s. These findings elucidate the concise and divergent biosynthesis of such intricate bridged polycyclic sesquiterpenoids, offer valuable biocatalysts for biotransformation, and highlight the distinct biosynthetic strategy employed by nature compared to chemical synthesis.

Genome Mining of Linaridins Provides Insights into the Widely Distributed LinC Oxidoreductases.

Linaridins are a family of underexplored ribosomally synthesized and post-translationally modified peptides despite the prevalence of their biosynthetic gene clusters (BGCs) in microbial genomes, as shown by bioinformatic studies. Our genome mining efforts reveal that 96 putative oxidoreductase genes, namely, LinC, are encoded in linaridin BGCs. We heterologously expressed two such LinC-containing linaridin BGCs, yan and ydn, from Streptomyces yunnanensis and obtained three new linaridins, named yunnanaridins A-C (1-3). Their structures are characterized by Z-configurations of the dehydrobutyrines and the presence of a variety of epimerized amino acid residues. Yunnanaridin A (1) is the sixth member of the family of type-B linaridins, whereas yunnanaridins B (2) and C (3) represent the first examples of expressed type-C linaridins. Interestingly, heterologous expression of the same BGCs with LinC in-frame knockouts produced the same compounds. This work expands the structural diversity of linaridins and provides evidence for the notion that the widespread LinCs may not be involved in linaridin biosynthesis.

Ursane and 24-Noroleanane-Type Triterpenoids with Anti-HIV Activity from the Twigs and Leaves of Antirhea chinensis.

Investigations on the twigs and leaves of Antirhea chinensis have led to the discovery of two undescribed pentacyclic triterpenoids (1 and 2) and nine known analogs. Compounds 1 and 2, each assigned as the ursane and 24-noroleanane-type triterpenoids, featuring similar oxidation pattern of 3ß,6ß,19α-trihydroxy-28-carboxyl. Their structures were elucidated via comprehensive analyses of spectroscopic data. Compound 1 displayed potent anti-HIV activity (EC50 =1.24 µM) and high selectivity index (SI >32.3).

Antimicrobial abietane-type diterpenoids from Torreya grandis.

Twelve undescribed abietane-type diterpenoids, along with ten known analogues were isolated from the twigs and leaves of Torreya grandis var. merrillii Hu. Their structures were characterized by spectroscopic data analyses, single-crystal X-ray diffraction, and ECD spectra. Torgranols A-C possess three different architectures shaped via a common 6,7-seco-procedure and subsequent ring formations. In particular, torgranol A represents the first example of a 6,7-seco-abietane diterpenoid featuring a unique oxygen bridge between C-3 and C-6. The biosynthetic pathways for torgranols A-C were proposed. Some compounds displayed antimicrobial activities against Mycobacterium tuberculosis and/or Staphylococcus aureus.

Lanthipeptides from the Same Core Sequence: Characterization of a Class II Lanthipeptide Synthetase from Microcystis aeruginosa NIES-88.

Class II lanthipeptide synthetases (LanMs) are relatively promiscuous to core peptide variations. Previous studies have shown that different LanMs catalyze identical reactions on the same core sequence fused to their respective cognate leaders. We characterized a new LanM enzyme from Microcystis aeruginosa NIES-88, MalM, and demonstrated that MalM and ProcM exhibited disparate dehydration and cyclization patterns on identical core peptides. Our study provided new insights into the regioselectivity of LanMs and showcased an appropriate strategy for lanthipeptide structural diversity engineering.

Biochemical Reconstitution Reveals the Biosynthetic Timing and Substrate Specificity for Thioamitides.

Thioamitides are apoptosis-inducing ribosomally synthesized and post-translationally modified peptides (RiPPs) with substantial post-translational modifications (PTMs), whose biosynthetic details remain elusive. We reconstituted their key PTMs through in vitro enzymatic reactions and gene coexpressions in E. coli and rigorously demonstrated the order of those modifications. Notably, thioamitide biosynthesis involves N- to C-terminal thioamidations and employs both leader-dependent and leader-independent reactions followed by leader removal by successive degradation. Our study provides a comprehensive overview of thioamitide biosynthesis and lays the foundation for thioamitide engineering in E. coli.

Cytotoxic Tigliane Diterpenoids from Croton damayeshu.

Chemical investigation of an EtOH extract of the twigs and leaves of Croton damayeshu afforded 10 new tigliane diterpenoids, crodamoids A-J (1-10), along with five known compounds. Their structures were elucidated by physical data analysis. Compounds 8, 9, and 15 displayed cytotoxic effects against two human tumor cell lines, A549 and HL-60 (IC50: 0.9-2.4 µM).

1,3-Bis(4-methyl-benz-yl)pyrimidine-2,4(1H,3H)-dione.

In the title mol-ecule, C(20)H(20)N(2)O(2), the central pyrimidine ring forms dihedral angles of 71.9 (1) and 69.8 (1)° with the two benzene rings. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into centrosymmetric dimers. The crystal packing exhibits also π-π inter-actions as indicated by short distances of 3.674 (2) Šbetween the centroids of the pyrimidine rings of neighbouring mol-ecules.