Inhibition of Mycobacterium tuberculosis dihydrodipicolinate synthase by alpha-ketopimelic acid and its other structural analogues

Sci Rep. 2016 Aug 9:6:30827. doi: 10.1038/srep30827.

Abstract

The Mycobacterium tuberculosis dihydrodipicolinate synthase (Mtb-dapA) is an essential gene. Mtb-DapA catalyzes the aldol condensation between pyruvate and L-aspartate-beta-semialdehyde (ASA) to yield dihydrodipicolinate. In this work we tested the inhibitory effects of structural analogues of pyruvate on recombinant Mtb-DapA (Mtb-rDapA) using a coupled assay with recombinant dihydrodipicolinate reductase (Mtb-rDapB). Alpha-ketopimelic acid (α-KPA) showed maximum inhibition of 88% and IC50 of 21 μM in the presence of pyruvate (500 μM) and ASA (400 μM). Competition experiments with pyruvate and ASA revealed competition of α-KPA with pyruvate. Liquid chromatography-mass spectrometry (LC-MS) data with multiple reaction monitoring (MRM) showed that the relative abundance peak of final product, 2,3,4,5-tetrahydrodipicolinate, was decreased by 50%. Thermal shift assays showed 1 °C Tm shift of Mtb-rDapA upon binding α-KPA. The 2.4 Å crystal structure of Mtb-rDapA-α-KPA complex showed the interaction of critical residues at the active site with α-KPA. Molecular dynamics simulations over 500 ns of pyruvate docked to Mtb-DapA and of α-KPA-bound Mtb-rDapA revealed formation of hydrogen bonds with pyruvate throughout in contrast to α-KPA. Molecular descriptors analysis showed that ligands with polar surface area of 91.7 Å(2) are likely inhibitors. In summary, α-hydroxypimelic acid and other analogues could be explored further as inhibitors of Mtb-DapA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspartic Acid / analogs & derivatives
  • Aspartic Acid / chemistry
  • Aspartic Acid / metabolism
  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Bridged-Ring Compounds / chemistry
  • Bridged-Ring Compounds / metabolism
  • Bridged-Ring Compounds / pharmacology*
  • Catalytic Domain
  • Crystallography, X-Ray
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Hydro-Lyases / antagonists & inhibitors
  • Hydro-Lyases / genetics
  • Hydro-Lyases / metabolism*
  • Hydrogen Bonding
  • Inhibitory Concentration 50
  • Ketones / chemistry
  • Ketones / metabolism
  • Ketones / pharmacology*
  • Kinetics
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / enzymology*
  • Pyruvic Acid / chemistry
  • Pyruvic Acid / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification

Substances

  • Bacterial Proteins
  • Bridged-Ring Compounds
  • Enzyme Inhibitors
  • Ketones
  • Recombinant Proteins
  • ketopinic acid
  • Aspartic Acid
  • aspartic semialdehyde
  • Pyruvic Acid
  • Hydro-Lyases
  • 4-hydroxy-tetrahydrodipicolinate synthase