Totopotensamide Congeners from a Halogenase-Inactivated Mutant

Area of Science:

• Natural Product Biosynthesis
• Enzymology
• Medicinal Chemistry

Background:

• Halogenases are crucial enzymes for modifying polyketide natural products, impacting their bioactivity and bioavailability.
• Totopotensamide A biosynthesis involves the halogenase TotH, responsible for C-4 chlorination, forming a nonproteinogenic amino acid.
• Understanding the structural diversity and bioactivity of halogenase-derived natural products is key to drug discovery.

Purpose of the Study:

• To isolate and characterize novel deschloro totopotensamide congeners from a totH-inactivated strain.
• To elucidate the structures and determine the absolute configurations of these new compounds.
• To evaluate the cytotoxic potential of the isolated deschloro totopotensamides against various cancer cell lines.

Main Methods:

• Isolation and structure elucidation of six new deschloro totopotensamide congeners (TPMs H2-H7).
• Determination of absolute configurations using a combination of J-based Nuclear Magnetic Resonance (J-NMR) analysis and bioinformatic approaches.
• In vitro cytotoxicity assays against A549, PANC-1, Calu3, and BXPC3 cancer cell lines.

Main Results:

• Six new deschloro totopotensamide congeners (compounds 5-10) were successfully isolated from the totH-inactivated strain.
• The absolute configuration of the polyketide chain in TPMs was proposed using compound 4 as a model.
• Compounds 5, 6, 8, and 9 exhibited significant cytotoxicity, with IC₅₀ values ranging from 2.3 to 9.7 μM.

Conclusions:

• The inactivation of the halogenase TotH leads to the production of diverse deschloro totopotensamide analogues.
• The study provides insights into the stereochemical diversity of totopotensamides.
• The identified cytotoxic deschloro totopotensamides represent potential leads for anticancer drug development.