Structure of the Dioxygenase AsqJ: Mechanistic Insights into a One-Pot Multistep Quinolone Antibiotic Biosynthesis

Angew Chem Int Ed Engl. 2016 Jan 4;55(1):422-6. doi: 10.1002/anie.201507835. Epub 2015 Nov 10.

Abstract

Multienzymatic cascades are responsible for the biosynthesis of natural products and represent a source of inspiration for synthetic chemists. The Fe(II)/α-ketoglutarate-dependent dioxygenase AsqJ from Aspergillus nidulans is outstanding because it stereoselectively catalyzes both a ferryl-induced desaturation reaction and epoxidation on a benzodiazepinedione. Interestingly, the enzymatically formed spiro epoxide spring-loads the 6,7-bicyclic skeleton for non-enzymatic rearrangement into the 6,6-bicyclic scaffold of the quinolone alkaloid 4'-methoxyviridicatin. Herein, we report different crystal structures of the protein in the absence and presence of synthesized substrates, surrogates, and intermediates that mimic the various stages of the reaction cycle of this exceptional dioxygenase.

Keywords: 4′-methoxyviridicatin; AsqJ dioxygenase; CH activation; alkaloids; biosynthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / biosynthesis*
  • Anti-Bacterial Agents / chemistry
  • Dioxygenases / chemistry*
  • Dioxygenases / metabolism
  • Models, Molecular
  • Molecular Structure
  • Quinolones / chemistry
  • Quinolones / metabolism*

Substances

  • Anti-Bacterial Agents
  • Quinolones
  • Dioxygenases