Molecules (Oct 2024)

Mechanism-Based Allylic Carbasugar Chlorides That Form Covalent Intermediates with α- and β-Galactosidases

  • Oluwafemi Akintola,
  • Sandeep Bhosale,
  • Andrew J. Bennet

DOI
https://doi.org/10.3390/molecules29204870
Journal volume & issue
Vol. 29, no. 20
p. 4870

Abstract

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Glycoside hydrolases have been implicated in a wide range of human conditions including lysosomal storage diseases. Consequently, many researchers have directed their efforts towards identifying new classes of glycoside hydrolase inhibitors, both synthetic and from natural sources. A large percentage of such inhibitors are reversible competitive inhibitors that bind in the active site often due to them possessing structural features, often a protonatable basic nitrogen atom, that mimic the enzymatic transition state. We report that mechanism-based small molecule galacto-like configured cyclohexenyl carbasugars form reversible covalent complexes with both α-galactosidase and β-galactosidase. In addition, we show that the β-galactosidase from Aspergillus oryzae reacts with three different carbasugar inhibitors, with three different second-order rate constants (kinact/Ki), to give the same enzyme–carbasugar covalent intermediate. The surprising observation that the α-galacto-configured inhibitor covalently labels the A. oryzae β-galactosidase highlights the catalytic versatility of glycoside hydrolases. We expect that cyclohexenyl covalent inhibitors will become an important class of compounds in the chemical biologist’s tool box.

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