Manno- epi-cyclophellitols Enable Activity-Based Protein Profiling of Human α-Mannosidases and Discovery of New Golgi Mannosidase II Inhibitors

J Am Chem Soc. 2020 Jul 29;142(30):13021-13029. doi: 10.1021/jacs.0c03880. Epub 2020 Jul 16.


Golgi mannosidase II (GMII) catalyzes the sequential hydrolysis of two mannosyl residues from GlcNAcMan5GlcNAc2 to produce GlcNAcMan3GlcNAc2, the precursor for all complex N-glycans, including the branched N-glycans associated with cancer. Inhibitors of GMII are potential cancer therapeutics, but their usefulness is limited by off-target effects, which produce α-mannosidosis-like symptoms. Despite many structural and mechanistic studies of GMII, we still lack a potent and selective inhibitor of this enzyme. Here, we synthesized manno-epi-cyclophellitol epoxide and aziridines and demonstrate their covalent modification and time-dependent inhibition of GMII. Application of fluorescent manno-epi-cyclophellitol aziridine derivatives enabled activity-based protein profiling of α-mannosidases from both human cell lysate and mouse tissue extracts. Synthesized probes also facilitated a fluorescence polarization-based screen for dGMII inhibitors. We identified seven previously unknown inhibitors of GMII from a library of over 350 iminosugars and investigated their binding modalities through X-ray crystallography. Our results reveal previously unobserved inhibitor binding modes and promising scaffolds for the generation of selective GMII inhibitors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cyclohexanols / chemical synthesis
  • Cyclohexanols / chemistry
  • Cyclohexanols / pharmacology*
  • Drug Discovery*
  • Enzyme Inhibitors / chemical synthesis
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Mannosidases / antagonists & inhibitors*
  • Mannosidases / metabolism
  • Molecular Structure


  • Cyclohexanols
  • Enzyme Inhibitors
  • cyclophellitol
  • Mannosidases
  • mannosyl-oligosaccharide 1,3 - 1,6-alpha-mannosidase