Poster Presentation The 46th Lorne Conference on Protein Structure and Function 2021

Inhibition studies of ketol-acid reductoisomerase from pathogenic microorganims (#309)

Shun Jie Wun 1 , Lambro Johnson 2 , Lv You 1 , Ross McGeary 1 , Thomas Brueck 3 , Gerhard Schenk 1 , Luke Guddat 1
  1. School of Chemistry and Molecular Biosciences, Australian Infectious Disease Research Centre, The University of Queensland, St Lucia, Queensland 4072, Australia
  2. School of Biomedical Sciences, The University of Queensland, St. Lucia, Queensland, 4072, Australia
  3. Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, University of Munich (TUM), Garching, Munich, Germany

Ketol-acid reductoisomerase (KARI), the second enzyme in the branched-chain amino acid (BCAA) biosynthesis pathway, is an emerging target for the discovery of biocides. Here, we demonstrate that cyclopropane-1,1- dicarboxylate (CPD) inhibits KARIs from the pathogens Mycobacterium tuberculosis (Mt) and Campylobacter jejuni (Cj) reversibly with Ki values of 3.03 μM and 0.59 μM, respectively. Another reversible inhibitor of both KARIs, Hoe 704, is more potent than CPD with Ki values of 300 nM and 110 nM for MtKARI and CjKARI, respectively. The most potent inhibitor tested here is N-hydroxy-N-isopropyloxamate (IpOHA). It has a Ki of ~26 nM for MtKARI, but binds rather slowly (kon ~900 M-1s-1). In contrast, IpOHA binds more rapidly (kon ~7000 M-1s-1) to CjKARI and irreversibly.