Slow-Binding Inhibition of Mycobacterium tuberculosis Shikimate Kinase by Manzamine Alkaloids

Johayra Simithy, Ngolui Rene Fuanta, Mansour Alturki, Judith V. Hobrath, Amir E. Wahba, Ivett Pina, Jnanendra Rath, Mark T. Hamann, Jack Deruiter, Douglas C. Goodwin, Angela I. Calderón (Lead / Corresponding author)

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9 Citations (Scopus)
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Abstract

Tuberculosis represents a significant public health crisis. There is an urgent need for novel molecular scaffolds against this pathogen. We screened a small library of marine-derived compounds against shikimate kinase from Mycobacterium tuberculosis (MtSK), a promising target for antitubercular drug development. Six manzamines previously shown to be active against M. tuberculosis were characterized as MtSK inhibitors: manzamine A (1), 8-hydroxymanzamine A (2), manzamine E (3), manzamine F (4), 6-deoxymanzamine X (5), and 6-cyclohexamidomanzamine A (6). All six showed mixed noncompetitive inhibition of MtSK. The lowest KI values were obtained for 6 across all MtSK-substrate complexes. Time-dependent analyses revealed two-step, slow-binding inhibition. The behavior of 1 was typical; initial formation of an enzyme-inhibitor complex (EI) obeyed an apparent KI of ∼30 μM with forward (k5) and reverse (k6) rate constants for isomerization to an EI∗ complex of 0.18 and 0.08 min-1, respectively. In contrast, 6 showed a lower KI for the initial encounter complex (∼1.5 μM), substantially faster isomerization to EI∗ (k5 = 0.91 min-1), and slower back conversion of EI∗ to EI (k6 = 0.04 min-1). Thus, the overall inhibition constants, KI∗, for 1 and 6 were 10 and 0.06 μM, respectively. These findings were consistent with docking predictions of a favorable binding mode and a second, less tightly bound pose for 6 at MtSK. Our results suggest that manzamines, in particular 6, constitute a new scaffold from which drug candidates with novel mechanisms of action could be designed for the treatment of tuberculosis by targeting MtSK.

Original languageEnglish
Pages (from-to)4923-4933
Number of pages11
JournalBiochemistry
Volume57
Issue number32
Early online date31 Jul 2018
DOIs
Publication statusPublished - 14 Aug 2018

Keywords

  • Mycobacterium tuberculosis
  • shikimate kinase
  • manzamine alkaloids
  • protein-ligand interactions
  • mass spectrometry
  • slow-binding inhibitor
  • jump dilution experiments
  • time-dependent inhibition
  • molecular docking

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