Covering: 2000 to 2017 Cytochrome P450 enzymes (P450s) are the most versatile biocatalysts in nature. The catalytic competence of these extraordinary hemoproteins is broadly harnessed by numerous chemical defenders such as bacteria, fungi, and plants for the generation of diverse and complex natural products. Rather than the common tailoring reactions (e.g. hydroxylation and epoxidation) mediated by the majority of biosynthetic P450s, in this review, we will focus on the unusual P450 enzymes in relation to new chemistry, skeleton construction, and structure re-shaping via their own unique catalytic power or the intriguing protein–protein interactions between P450s and other proteins. These uncommon P450 reactions lead to a higher level of chemical space expansion for natural products, through which a broader spectrum of bioactivities can be gained by the host organisms.

P450s play crucial roles in fungal natural product biosynthesis by mediating various common and uncommon reactions.

Diterpene synthase VenA is responsible for assembling venezuelaene A with a unique 5-5-6-7 tetracyclic skeleton from geranylgeranyl pyrophosphate. VenA also demonstrates substrate promiscuity by accepting geranyl pyrophosphate and farnesyl pyrophosphate as alternative substrates. Herein, we report the crystal structures of VenA in bothapoform andholoform in complex with a trinuclear magnesium cluster and pyrophosphate group. Functional and structural investigations on the atypical¹¹⁵DSFVSD¹²⁰motif of VenA,versusthe canonical Asp-rich motif of DDXX(X)D/E, reveal that the absent second Asp of canonical motif is functionally replaced by Ser116 and Gln83, together with bioinformatics analysis identifying a hidden subclass of type I microbial terpene synthases. Further structural analysis, multiscale computational simulations, and structure-directed mutagenesis provide significant mechanistic insights into the substrate selectivity and catalytic promiscuity of VenA. Finally, VenA is semi-rationally engineered into a sesterterpene synthase to recognize the larger substrate geranylfarnesyl pyrophosphate.

Most P450s require redox partners for the electron transfer during catalysis. However, little information is available on cognate redox partners for P450s, which greatly limits P450 function exploration and practical application. Thus, the stategy of building various hybrid P450 catalytic systems with surrogate redox partner has often adopted to engineer P450 biocatalysts. In this study, we compare three pairs of frequently-used surrogate redox partner SelFdx1499/SelFdR0978, Adx/AdR and Pdx/PdR and in terms of their electron transfer properties. The three selected bacterial Class I P450s include PikC, P450sca-2 and CYP-sb21, which are responsible for production of high-value-added products. Here we show that SelFdx1499/SelFdR0978 is the most promising redox partner compared to Adx/AdR and Pdx/PdR. The results provide insights into the domination for P450-redox partner interactions in modulating the catalytic activity of P450s. This study not only produces a more active biocatalyst but also suggests a general chose for a universal reductase which would facilitate engineering of P450 catalyst.

Marine-derived fungi are a rich source of structurally diverse metabolites. Fungi produce an array of compounds when grown under different cultivation conditions. In the present work, different media were used to cultivate the fungus Aspergillus sp. ZA-01, which was previously studied for the production of bioactive compounds, and three new prenylxanthone derivatives, aspergixanthones I–K (1–3), and four known analogues (4–7) were obtained. The absolute configuration of 1 was assigned by ECD experiment and the Mo₂(AcO)₄ ICD spectrum of its methanolysis derivative (1a). All the compounds (1–7) were evaluated for their anti-Vibrio activities. Aspergixanthone I (1) showed the strongest anti-Vibrio activity against Vibrio parahemolyticus (MIC = 1.56 μM), Vibrio anguillarum (MIC = 1.56 μM), and Vibrio alginolyticus (MIC = 3.12 μM).

A chemical investigation was conducted on the aerial parts of the mangrove plant Sonneratia paracaseolaris, yielding five new triterpenoid paracaseolins A–E (1–4, and 11) together with twelve known analogues (5–10, 12–17). Their structures were established by extensive spectroscopic methods and comparisons their spectroscopic data with those of the known related compounds. The cytotoxicities against P388, HeLa, A549, and K562 tumor cell lines and anti-H1N1 (Influenza A virus) activities for the isolates were evaluated. Compound 4 showed potent cytotoxicity against the A549 cell line with an IC₅₀ value of 1.89 µM, and compound 1 exhibited significant anti-H1N1 virus activity with an IC₅₀ value of 28.4 µg/mL. A preliminary structure activity relationship was discussed.